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So I'm using an app that stores images heavily in the DB. What's your outlook on this? I'm more of a type to store the location in the filesystem, than store it directly in the DB.
What do you think are the pros/cons?
I'm in charge of some applications that manage many TB of images. We've found that storing file paths in the database to be best.
There are a couple of issues:
database storage is usually more expensive than file system storage
you can super-accelerate file system access with standard off the shelf products
for example, many web servers use the operating system's sendfile() system call to asynchronously send a file directly from the file system to the network interface. Images stored in a database don't benefit from this optimization.
things like web servers, etc, need no special coding or processing to access images in the file system
databases win out where transactional integrity between the image and metadata are important.
it is more complex to manage integrity between db metadata and file system data
it is difficult (within the context of a web application) to guarantee data has been flushed to disk on the filesystem
As with most issues, it's not as simple as it sounds. There are cases where it would make sense to store the images in the database.
You are storing images that are
changing dynamically, say invoices and you wanted
to get an invoice as it was on 1 Jan
2007?
The government wants you to maintain 6 years of history
Images stored in the database do not require a different backup strategy. Images stored on filesystem do
It is easier to control access to the images if they are in a database. Idle admins can access any folder on disk. It takes a really determined admin to go snooping in a database to extract the images
On the other hand there are problems associated
Require additional code to extract
and stream the images
Latency may be
slower than direct file access
Heavier load on the database server
File store. Facebook engineers had a great talk about it. One take away was to know the practical limit of files in a directory.
Needle in a Haystack: Efficient Storage of Billions of Photos
This might be a bit of a long shot, but if you're using (or planning on using) SQL Server 2008 I'd recommend having a look at the new FileStream data type.
FileStream solves most of the problems around storing the files in the DB:
The Blobs are actually stored as files in a folder.
The Blobs can be accessed using either a database connection or over the filesystem.
Backups are integrated.
Migration "just works".
However SQL's "Transparent Data Encryption" does not encrypt FileStream objects, so if that is a consideration, you may be better off just storing them as varbinary.
From the MSDN Article:
Transact-SQL statements can insert, update, query, search, and back up FILESTREAM data. Win32 file system interfaces provide streaming access to the data.
FILESTREAM uses the NT system cache for caching file data. This helps reduce any effect that FILESTREAM data might have on Database Engine performance. The SQL Server buffer pool is not used; therefore, this memory is available for query processing.
File paths in the DB is definitely the way to go - I've heard story after story from customers with TB of images that it became a nightmare trying to store any significant amount of images in a DB - the performance hit alone is too much.
In my experience, sometimes the simplest solution is to name the images according to the primary key. So it's easy to find the image that belongs to a particular record, and vice versa. But at the same time you're not storing anything about the image in the database.
The trick here is to not become a zealot.
One thing to note here is that no one in the pro file system camp has listed a particular file system. Does this mean that everything from FAT16 to ZFS handily beats every database?
No.
The truth is that many databases beat many files systems, even when we're only talking about raw speed.
The correct course of action is to make the right decision for your precise scenario, and to do that, you'll need some numbers and some use case estimates.
In places where you MUST guarantee referential integrity and ACID compliance, storing images in the database is required.
You cannot transactionaly guarantee that the image and the meta-data about that image stored in the database refer to the same file. In other words, it is impossible to guarantee that the file on the filesystem is only ever altered at the same time and in the same transaction as the metadata.
As others have said SQL 2008 comes with a Filestream type that allows you to store a filename or identifier as a pointer in the db and automatically stores the image on your filesystem which is a great scenario.
If you're on an older database, then I'd say that if you're storing it as blob data, then you're really not going to get anything out of the database in the way of searching features, so it's probably best to store an address on a filesystem, and store the image that way.
That way you also save space on your filesystem, as you are only going to save the exact amount of space, or even compacted space on the filesystem.
Also, you could decide to save with some structure or elements that allow you to browse the raw images in your filesystem without any db hits, or transfer the files in bulk to another system, hard drive, S3 or another scenario - updating the location in your program, but keep the structure, again without much of a hit trying to bring the images out of your db when trying to increase storage.
Probably, it would also allow you to throw some caching element, based on commonly hit image urls into your web engine/program, so you're saving yourself there as well.
Small static images (not more than a couple of megs) that are not frequently edited, should be stored in the database. This method has several benefits including easier portability (images are transferred with the database), easier backup/restore (images are backed up with the database) and better scalability (a file system folder with thousands of little thumbnail files sounds like a scalability nightmare to me).
Serving up images from a database is easy, just implement an http handler that serves the byte array returned from the DB server as a binary stream.
Here's an interesting white paper on the topic.
To BLOB or Not To BLOB: Large Object Storage in a Database or a Filesystem
The answer is "It depends." Certainly it would depend upon the database server and its approach to blob storage. It also depends on the type of data being stored in blobs, as well as how that data is to be accessed.
Smaller sized files can be efficiently stored and delivered using the database as the storage mechanism. Larger files would probably be best stored using the file system, especially if they will be modified/updated often. (blob fragmentation becomes an issue in regards to performance.)
Here's an additional point to keep in mind. One of the reasons supporting the use of a database to store the blobs is ACID compliance. However, the approach that the testers used in the white paper, (Bulk Logged option of SQL Server,) which doubled SQL Server throughput, effectively changed the 'D' in ACID to a 'd,' as the blob data was not logged with the initial writes for the transaction. Therefore, if full ACID compliance is an important requirement for your system, halve the SQL Server throughput figures for database writes when comparing file I/O to database blob I/O.
One thing that I haven't seen anyone mention yet but is definitely worth noting is that there are issues associated with storing large amounts of images in most filesystems too. For example if you take the approach mentioned above and name each image file after the primary key, on most filesystems you will run into issues if you try to put all of the images in one big directory once you reach a very large number of images (e.g. in the hundreds of thousands or millions).
Once common solution to this is to hash them out into a balanced tree of subdirectories.
Something nobody has mentioned is that the DB guarantees atomic actions, transactional integrity and deals with concurrency. Even referentially integrity is out of the window with a filesystem - so how do you know your file names are really still correct?
If you have your images in a file-system and someone is reading the file as you're writing a new version or even deleting the file - what happens?
We use blobs because they're easier to manage (backup, replication, transfer) too. They work well for us.
The problem with storing only filepaths to images in a database is that the database's integrity can no longer be forced.
If the actual image pointed to by the filepath becomes unavailable, the database unwittingly has an integrity error.
Given that the images are the actual data being sought after, and that they can be managed easier (the images won't suddenly disappear) in one integrated database rather than having to interface with some kind of filesystem (if the filesystem is independently accessed, the images MIGHT suddenly "disappear"), I'd go for storing them directly as a BLOB or such.
At a company where I used to work we stored 155 million images in an Oracle 8i (then 9i) database. 7.5TB worth.
Normally, I'm storngly against taking the most expensive and hardest to scale part of your infrastructure (the database) and putting all load into it. On the other hand: It greatly simplifies backup strategy, especially when you have multiple web servers and need to somehow keep the data synchronized.
Like most other things, It depends on the expected size and Budget.
We have implemented a document imaging system that stores all it's images in SQL2005 blob fields. There are several hundred GB at the moment and we are seeing excellent response times and little or no performance degradation. In addition, fr regulatory compliance, we have a middleware layer that archives newly posted documents to an optical jukebox system which exposes them as a standard NTFS file system.
We've been very pleased with the results, particularly with respect to:
Ease of Replication and Backup
Ability to easily implement a document versioning system
If this is web-based application then there could be advantages to storing the images on a third-party storage delivery network, such as Amazon's S3 or the Nirvanix platform.
Assumption: Application is web enabled/web based
I'm surprised no one has really mentioned this ... delegate it out to others who are specialists -> use a 3rd party image/file hosting provider.
Store your files on a paid online service like
Amazon S3
Moso Cloud Storage
Another StackOverflow threads talking about this here.
This thread explains why you should use a 3rd party hosting provider.
It's so worth it. They store it efficiently. No bandwith getting uploaded from your servers to client requests, etc.
If you're not on SQL Server 2008 and you have some solid reasons for putting specific image files in the database, then you could take the "both" approach and use the file system as a temporary cache and use the database as the master repository.
For example, your business logic can check if an image file exists on disc before serving it up, retrieving from the database when necessary. This buys you the capability of multiple web servers and fewer sync issues.
I'm not sure how much of a "real world" example this is, but I currently have an application out there that stores details for a trading card game, including the images for the cards. Granted the record count for the database is only 2851 records to date, but given the fact that certain cards have are released multiple times and have alternate artwork, it was actually more efficient sizewise to scan the "primary square" of the artwork and then dynamically generate the border and miscellaneous effects for the card when requested.
The original creator of this image library created a data access class that renders the image based on the request, and it does it quite fast for viewing and individual card.
This also eases deployment/updates when new cards are released, instead of zipping up an entire folder of images and sending those down the pipe and ensuring the proper folder structure is created, I simply update the database and have the user download it again. This currently sizes up to 56MB, which isn't great, but I'm working on an incremental update feature for future releases. In addition, there is a "no images" version of the application that allows those over dial-up to get the application without the download delay.
This solution has worked great to date since the application itself is targeted as a single instance on the desktop. There is a web site where all of this data is archived for online access, but I would in no way use the same solution for this. I agree the file access would be preferable because it would scale better to the frequency and volume of requests being made for the images.
Hopefully this isn't too much babble, but I saw the topic and wanted to provide some my insights from a relatively successful small/medium scale application.
SQL Server 2008 offers a solution that has the best of both worlds : The filestream data type.
Manage it like a regular table and have the performance of the file system.
It depends on the number of images you are going to store and also their sizes. I have used databases to store images in the past and my experience has been fairly good.
IMO, Pros of using database to store images are,
A. You don't need FS structure to hold your images
B. Database indexes perform better than FS trees when more number of items are to be stored
C. Smartly tuned database perform good job at caching the query results
D. Backups are simple. It also works well if you have replication set up and content is delivered from a server near to user. In such cases, explicit synchronization is not required.
If your images are going to be small (say < 64k) and the storage engine of your db supports inline (in record) BLOBs, it improves performance further as no indirection is required (Locality of reference is achieved).
Storing images may be a bad idea when you are dealing with small number of huge sized images. Another problem with storing images in db is that, metadata like creation, modification dates must handled by your application.
I have recently created a PHP/MySQL app which stores PDFs/Word files in a MySQL table (as big as 40MB per file so far).
Pros:
Uploaded files are replicated to backup server along with everything else, no separate backup strategy is needed (peace of mind).
Setting up the web server is slightly simpler because I don't need to have an uploads/ folder and tell all my applications where it is.
I get to use transactions for edits to improve data integrity - I don't have to worry about orphaned and missing files
Cons:
mysqldump now takes a looooong time because there is 500MB of file data in one of the tables.
Overall not very memory/cpu efficient when compared to filesystem
I'd call my implementation a success, it takes care of backup requirements and simplifies the layout of the project. The performance is fine for the 20-30 people who use the app.
Im my experience I had to manage both situations: images stored in database and images on the file system with path stored in db.
The first solution, images in database, is somewhat "cleaner" as your data access layer will have to deal only with database objects; but this is good only when you have to deal with low numbers.
Obviously database access performance when you deal with binary large objects is degrading, and the database dimensions will grow a lot, causing again performance loss... and normally database space is much more expensive than file system space.
On the other hand having large binary objects stored in file system will cause you to have backup plans that have to consider both database and file system, and this can be an issue for some systems.
Another reason to go for file system is when you have to share your images data (or sounds, video, whatever) with third party access: in this days I'm developing a web app that uses images that have to be accessed from "outside" my web farm in such a way that a database access to retrieve binary data is simply impossible. So sometimes there are also design considerations that will drive you to a choice.
Consider also, when making this choice, if you have to deal with permission and authentication when accessing binary objects: these requisites normally can be solved in an easier way when data are stored in db.
I once worked on an image processing application. We stored the uploaded images in a directory that was something like /images/[today's date]/[id number]. But we also extracted the metadata (exif data) from the images and stored that in the database, along with a timestamp and such.
In a previous project i stored images on the filesystem, and that caused a lot of headaches with backups, replication, and the filesystem getting out of sync with the database.
In my latest project i'm storing images in the database, and caching them on the filesystem, and it works really well. I've had no problems so far.
Second the recommendation on file paths. I've worked on a couple of projects that needed to manage large-ish asset collections, and any attempts to store things directly in the DB resulted in pain and frustration long-term.
The only real "pro" I can think of regarding storing them in the DB is the potential for easy of individual image assets. If there are no file paths to use, and all images are streamed straight out of the DB, there's no danger of a user finding files they shouldn't have access to.
That seems like it would be better solved with an intermediary script pulling data from a web-inaccessible file store, though. So the DB storage isn't REALLY necessary.
The word on the street is that unless you are a database vendor trying to prove that your database can do it (like, let's say Microsoft boasting about Terraserver storing a bajillion images in SQL Server) it's not a very good idea. When the alternative - storing images on file servers and paths in the database is so much easier, why bother? Blob fields are kind of like the off-road capabilities of SUVs - most people don't use them, those who do usually get in trouble, and then there are those who do, but only for the fun of it.
Storing an image in the database still means that the image data ends up somewhere in the file system but obscured so that you cannot access it directly.
+ves:
database integrity
its easy to manage since you don't have to worry about keeping the filesystem in sync when an image is added or deleted
-ves:
performance penalty -- a database lookup is usually slower that a filesystem lookup
you cannot edit the image directly (crop, resize)
Both methods are common and practiced. Have a look at the advantages and disadvantages. Either way, you'll have to think about how to overcome the disadvantages. Storing in database usually means tweaking database parameters and implement some kind of caching. Using filesystem requires you to find some way of keeping filesystem+database in sync.
Although this question has been appear in past previous post, but different scenario and different consideration decide which one is the best.
I need to implement a system whereby it can handle 200GB - 400GB size of images yearly(approximately < 1mb per image). It is P&C images which only allowed for authorised personal to access and VIEW only. I am planning to use an application based of system to INSERT to MYSQL database and using PHP web based application for VIEW only.
I am thinking to use FILESYSTEM because it is easy to do backup & restore on the images and no need to worry on the size of the MYSQL database.
I am using MySQL + Apache + PHP running in Windows Server.
Your advice and input is very much appreciated.
Thank you.
Regards,
Desmond
Also worth reading:
Best Practice in File Storage while Building Applications - Database (Blob Storage) Vs File System
BLOB Storage as the Best Solution
For better scalability. Although file systems are designed to handle a large number of objects of varying sizes, say files and folders, actually they are not optimized for a huge number (tens of millions) of small files. Database systems are optimized for such scenarios.
For better availability. Database servers have availability features that extend beyond those provided by the file system. Database replication is a set of solutions that allow you to copy, distribute, and potentially modify data in a distributed environment whereas Log shipping provides a way of keeping a stand-by copy of a database in case the primary system fails.
For central repository of data with controlled growth. DBA has the privilege to control and monitor the growth of database and split the database as and when needed.
For full-text index and search operations. You can index and search certain types of data stored in BLOB columns. When a database designer decides that a table will contain a BLOB column and the column will participate in a full-text index, the designer must create, in the same table, a separate character-based data column that will hold the file extension of the file in the corresponding BLOB field. During the full-text indexing operation, the full-text service looks at the extensions listed in the character-based column (.txt, .doc, .xls, etc.), applies the corresponding filter to interpret the binary data, and extracts the textual information needed for indexing and querying.
File System Storage as the Best Solution
For the application in which the images will be used requires streaming performance, such as real-time video playback.
For applications such as Microsoft PhotoDraw® or Adobe PhotoShop, which only know how to access files.
If you want to use some specific feature in the NTFS file system such as Remote Storage.
objects smaller than 256K are best stored in a database while objects
larger than 1M are best stored in the filesystem. Between 256K and 1M,
the read:write ratio and rate of object overwrite or replacement are
important factors.
souce:
http://research.microsoft.com/apps/pubs/default.aspx?id=64525
Edit: It is MS SQL, so MAYBE same as Mysql :)
I have a question about the blob data type in MySQL.
I read that the data type can be used to store files. I also read that an alternative is to store the file on disk and include a pointer to its location in the database (via a varchar column).
But I'm a little confused because I've read that blob fields are not stored in-row and require a separate look-up to retrieve its contents. So is that any different than storing a pointer to a file on the file system?
I read that the data type can be used to store files.
According to MySQL manual page on Blob, A BLOB is a binary large object that can hold a variable amount of data.
Since it's a data type specific to store binary data it's common to use it to store files in binary format, being storing image files a very common use on web applications.
For web applications this would mean that you would first need to convert your file into binary format and then store it, and every time you need to retrieve your file you would need to do the reverse process of converting them back to it's original format.
Besides that, storing large amount of data in your db MAY slow it down. Specially in systems that are not dedicated only to host a database.
I also read that an alternative is to store the file on disk and include a pointer to its location in the database
Bearing in mind all above considerations a common practice for web applications is to store your files elsewhere than your MySQL and then simply store it's path on your database. This approach MAY speed up your database when dealing with large amount of data.
But I'm a little confused because I've read that blob fields are not stored in-row and require a separate look-up to retrieve its contents.
In fact that would depend on what storage engine you are using since every engine treats data and stores it in different ways. For the InnoDB engine, which is suited for relational database you may want to read this article from MySQL Performance blog on how the blob is stored in MySQL.
But in abstract, on MySQL 5 and forward the blob is stored as following:
Innodb stores either whole blob on the row page or only 20 bytes BLOB pointer giving preference to smaller columns to be stored on the page, which is reasonable as you can store more of them.
So you are probably thinking now that the right way to go is to store them as separate file, but there are some advantages of using blob to store data, the first one (in my opinion) is the backup. I manage a small server and I had to create another subroutine only to copy my files stored as paths to another storage disk (We couldn't afford to buy a decent tape backup system). If I had designed my application to use blobs a simple mysqldump would be everything that I needed to backup my whole database.
The advantage of storing blobs for backups are better discussed on this post where the person who answered had a similar problem than mine.
Another advantage is security and the easiness of managing permission and access. All the data inside your MySQL server is password protected and you can easily manage permissions for your users about who access what and who doesn't.
In a application which relies on MySQL privileges system for authentication and use. It's certain a plus since it would be a little harder for let's say an invader to retrieve an image (or a binary file like a zipped one) from your disk or an user without access privileges to access it.
So I'd say that
If you gonna manage your MySQL and all the data you have in it and must do regular backups or intend to change or even consider a future change of OS, and have a decent hardware and optimized your MySQL to it, go for BLOB.
If you will not manage your MySQL (as in a web host for example) and doesn't intend to change OS or make backups, stick with varchar columns pointing to your files.
I hope it helped. Cheers
If you store data is BLOB field, you are making it part of your object abstraction.
BLOB advantages:
Should you want to remove row with BLOB, or remove it as part of master/slave table relationship or maybe the whole table hierarchy, your BLOB is handled automatically and has same lifetime as any other object in database.
Your scripts do not have a need to access anything but database to get everything they require. In many situations, having direct file access open whole can of worms on how to bypass access or security restrictions. For example, with file access, they may have to mount filesystems which contain actual files. But with BLOB in database, you only have to be able to connect to database, no matter where you are.
If you store it in file and file is replaced, removed or no longer accessible, your database would never know - in effect, you cannot guarantee integrity. Also, it is difficult to reliably support multiple versions when using files. If you use and depend on transactions, it becomes almost impossible.
File advantages:
Some databases handle BLOBs rather poorly. For example, while official BLOB limit in MySQL is 4GB, but in reality it is only 1MB in default configuration. You can increase this to 16-32MB by tweaking both client and server configuration to increase MySQL command buffer, but this has a lot of other implications in terms of performance and security.
Even if database does not have some weird size limits, it always will have some overhead in storing BLOB compared to just a file. Also, if BLOB is large, some databases do not provide interface to access blob piece by piece, or stream it, which can be large impediment for your workflow.
In the end, it is up to you. I typically try to keep it in BLOB, unless this creates unreasonable performance problems.
Yes, MySQL blobs that don't fit within the same page as a row get stored on overflow pages Note that some blobs are small enough that they're stored with the rest of the row, like any other column. The blob pages are not adjacent to the page their row is stored on, so they may result in extra I/O to read them.
On the other hand, just like with any other page type, blob pages can occupy memory in the InnoDB buffer pool, so reading the blobs subsequently is very fast even if they are on separate pages. Files can be cached by the operating system, but typically they're read from disk.
Here are a few other factors that may affect your decision:
Blobs are stored logically with a row. This means if you DELETE the row, the associated blob is deleted automatically. But if you store the blob outside the database, you end up with orphaned blob files after you delete rows from the database. You have to do manual steps to find and delete these files.
Blobs stored in the row also follow transaction semantics. For instance, a new blob or an updated blob is invisible to other transactions until you commit. You can also roll back a change. Storing blobs in files outside the database makes this a lot harder.
When you back up a database containing blobs, the database is a lot bigger of course, but when you backup, you get all the data and associated blobs in one step. If you store blobs externally, you have to back up the database and also back up the filesystem where you store blob files. If you need to ensure that the data and blobs are captured from one instant in time, you pretty much need to use some kind of filesystem snapshots.
If you use replication, the only automatic way of ensuring the blobs get copied to the replication slave automatically is to store blobs in the database.
Filesystem access will be faster than through the database. Blobs columns have some disadvantages in terms of indexing/sorting etc, which you could do with your filename column if you wished to in the future.
The database can also grow quickly with large blobs and then tasks like backing up become slower. I would go with a file location in database with the physical storage on the file system.
The better approach is to store your file in the filesystem folder and point to their paths through a varchar field in the database. One of the drawbacks of saving files in the database is slowing it or reducing its performance.
I have an application where customers upload files like Powerpoints and Excel spreadsheets to the application through a web UI. The files then have meta data associated with them and they are stored as BLOBs in a MySQL database. The users may download these files occasionally, but not very often. The emphasis here is on archiving. Security of data is also important.
If that is the case, what are the pros and cons of storing the files as BLOBs in MySQL as opposed to putting them on Amazon S3? I've never used S3 before but hear that it's popular for storing files.
The main advantage of relational databases (such as MySQL) is the elegance it permits you to query for data. BLOB columns, however, offer very little in terms of rich query semantics compared to other column types, so If that's your main use case, there's hardly any reason to use a relational database at all, it doesn't offer much above and beyond a regular filesystem or simple key-value datastore (such as s3).
Dollars to bytes, s3 is likely much more cost effective.
On the other hand, there are some things that a relational database can bring that would be worhtwhile. The most obvious is transactional semantics (only on the InnoDB engine, not available with MyISAM), so that you can safely know that whole groups of uploads or modifications take place consistencly. Another advantage is that you can still add metadata about your blobs (even if it's only over time, as your application improves) so you can still benefit some from the rich queries MySQL supports.
storing binary data into blob
make your database fat
size limitation (is overcome at the later version in mysql)
data portability is not there (you need a mysql api/client to access the data)
there is no true security
If you are archiving the binary data,
store into normal disk file
If security is important,
consider separate between your UI server and storage server,
but is hard to archive,
you can always consider to embed password / encryption into these binary files
security over amazon s3
http://docs.amazonwebservices.com/AmazonS3/latest/dev/index.html?UsingAuthAccess.html
http://docs.amazonwebservices.com/AmazonS3/latest/dev/index.html?S3_QSAuth.html
Security of data is also important.
Do note that files on S3 are not stored on encrypted disks, so you may have to encrypt client-side or on your servers before sending it up to S3.
I've been storing data in S3 for years and completely love it! What I do is upload the file to S3 (where its copied multiple times by the way) and then store a reference to the file path and name into my MySQL files table. If anything else, it takes that much load off of the MySQL DB and S3 now offers AES256 bit encryption with revolving master keys so you know its secure!