I would like to know whether there is any thing at the OS level to look at and tune which could help for the mysql that will be installed in next step.
I know a few things to consider like
file system: some file systems will fit better for mysql and its engines
behavior
open file : We should be able to open enough number of file as MYISAM
opens 3 files for each table
Architecture : 64 bit is recommended than 32 bit.
What else I can tune or consider here.
THanks in advacen....
Related
I have MySQL 5.7.24 running on a Windows VM. It has a few thousand databases (7000). I understand this is not the recommended set up for MySQL but some business requirements have necessitated this multi-tenant db structure and I cannot change that unfortunately.
The server works fine when it is running but the startup time can get pretty long, almost 20-30 mins after a clean shutdown of the MySQL service and 1+ hours after a restart of the Windows VM.
Is there any way to reduce the startup time?
In my configuration, I observed that innodb_file_per_table = ON (which is the default for MySQL 5.7 I believe) and so I think that at startup it is scanning every .ibd file.
Would changing innodb_file_per_table = OFF and then altering each table to get rid of the .ibd files be a viable option. One thing to note is that in general, every database size is pretty small and even with 7000 databases, the total size of the data is about 60gb only. So to my understanding, innodb_file_per_table = ON is more beneficial when there are single tables that can get pretty large which is not the case for my server.
Question: Is my logic reasonable and could this innodb_file_per_table be the reason for the slow startup? Or is there some other config variable that I can change so that each .ibd file is not scanned before the server starts accepting connections.
Any help to guide me in the right direction would be much appreciated. Thanks in advance!
You should upgrade to MySQL 8.0.
I was working on a system with the same problem as yours. In our case, we had about 1500 schemas per MySQL instance, and a little over 100 tables per schema. So it was about 160,000+ tables per instance. It caused lots of problems trying to use innodb_file_per_table, because the mysqld process couldn't work with that many open file descriptors efficiently. The only way to make the system work was to abandon file-per-table, and move all the tables into the central tablespace.
But that causes a different problem. Tablespaces never shrink, they only grow. The only way to shrink a tablespace is to move the tables to another tablespace, and drop the big one.
One day one of the developers added some code that used a table like a log, inserting a vast number of rows very rapidly. I got him to stop logging that data, but by then it was too late. MySQL's central tablespace had expanded to 95% of the size of the database storage, leaving too little space for binlogs and other files. And I could never shrink it without incurring downtime for our business.
I asked him, "Why were you writing to that table so much? What are you doing with the data you're storing?" He shrugged and said casually, "I dunno, I thought the data might be interesting sometime, but I had no specific use for them." I felt like strangling him.
The point of this story is that one naïve developer can cause a lot of inconvenience if you disable innodb_file_per_table.
When MySQL 8.0 was being planned, the MySQL Product Manager solicited ideas for scalability criteria. I told him about the need to support instances with a lot of tables, like 160k or more. MySQL 8.0 included an all-new implementation of internal code for handling metadata about tables, and he asked the engineers to test the scalability with up to 1 million tables (with file-per-table enabled).
So the best solution to your problem is not to turn off innodb_file_per_table. That will just lead to another kind of crisis. The best solution is to upgrade to 8.0.
Re your comment:
As far as I know, InnoDB does not open tables at startup time. It opens tables when they are first queried.
Make sure you have table_open_cache and innodb_open_files tuned for your scale. Here is some reading:
https://dev.mysql.com/doc/refman/5.7/en/table-cache.html
https://www.percona.com/blog/2009/11/18/how-innodb_open_files-affects-performance/
https://www.percona.com/blog/2018/11/28/what-happens-if-you-set-innodb_open_files-higher-than-open_files_limit/
https://www.percona.com/blog/2017/10/01/one-million-tables-mysql-8-0/
I hope you are using an SSD for storage, not a spinning disk. This makes a huge difference when doing a lot of small I/O operations. SSD storage devices have been a standard recommendation for database servers for about 10 years.
Also this probably doesn't help you but I gave up on using Windows around 2007. Not as a server nor a desktop.
I have looked all over the MySQL website and found no definitive answers.
Is the size of the database determined by the operating system or is there 4GB limit?
Where can I find perforamnce statistics against other databases (sqlServer, oracle ect)
According to the MySQL Manual:
E.10.3. Limits on Table Size
The effective maximum table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits. The following table lists some examples of operating system file-size limits. This is only a rough guide and is not intended to be definitive. For the most up-to-date information, be sure to check the documentation specific to your operating system.
Operating System File-size Limit
Win32 w/ FAT/FAT32 2GB/4GB
Win32 w/ NTFS 2TB (possibly larger)
Linux 2.2-Intel 32-bit 2GB (LFS: 4GB)
Linux 2.4+ (using ext3 file system) 4TB
Solaris 9/10 16TB
MacOS X w/ HFS+ 2TB
Windows users, please note that FAT and VFAT (FAT32) are not considered suitable for production use with MySQL. Use NTFS instead.
On Linux 2.2, you can get MyISAM tables larger than 2GB in size by using the Large File Support (LFS) patch for the ext2 file system. Most current Linux distributions are based on kernel 2.4 or higher and include all the required LFS patches. On Linux 2.4, patches also exist for ReiserFS to get support for big files (up to 2TB). With JFS and XFS, petabyte and larger files are possible on Linux.
As for the other part of your question, a few thoughts:
It's a broad, complex, multi-factorial question. Consider narrowing the scope of the question to MySQL and one other RDBMS (eg. SQL Server) and probably even one particular feature.
Google is your friend.
Vendors tend to publish their own biased comparisons. Take vendor numbers with a grain of salt.
1- With respect to database size, the limit is dependent on Operating System file size. Please see this article
2- The effective maximum table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits. (Source)
3- You may google for MySQL vs SQL Server Vs Oracle, also check this link
default mysql is 256 TB for myd file with 6 byte pointer size. i know this is ridiculous answer, but that is what you wanted to know. in real life all depends on the queries, indexes, column count, row count, etc.. i guess.
With today's hardware and OS, together with MySQL's preferred Engine InnoDB, the table size limitation is 64TB. With PARTITIONing, that can be stretched to over a hundred petabytes.
A database is a collection of tables. So, to answer the title question literally, we need to go beyond the max table size. Since there can be thousands of tables in a database, we are now into the exabyte stratosphere.
See also Hard limits in MySQL .
I'm trying to build a dev copy of a production MySQL database by loading one of the backups. How long should it take to do this if the uncompressed dump is ~20G?
This command has been running for something like 24h with 10% CPU load and I'm wondering if it's just slow or if it/I am doing something wrong.
mysql -u root -p < it_mysql_dump.sql
BTW it's on a beefy desktop dev machine with plenty of ram, but it might be reading and writing the same HDD. I think I'm using InnoDB.
Restoring MySQL dumps can take a long time. This is because it does really rebuild the entire tables.
Exactly what you need to do to fix it depends on the engine, but in general
I would say, do the following:
Zeroth rule: Only use a 64-bit OS.
Make sure that you have enough physical ram to fit the biggest single table into memory; include any overhead for the OS in this calculation (NB: On operating systems that use 4k pages i.e. all of them, the page tables take up a lot of memory themselves on large-memory systems - don't forget this)
Tune the innodb_buffer_pool such that it is bigger than the largest single table; or if using MyISAM, tune the key_buffer so that it is big enough to hold the indexes of the largest table.
Be patient.
Now, if you are still finding that it is slow having done the above, it may be that your particular database has a very tricky structure to restore.
Personally I've managed to rebuild a server with ~ 2Tb in < 48 hours, but that was a particular case.
Be sure that your development system has production-grade hardware if you intend to load production data into it.
In particular, if you think that you can bulk-load data into tables which don't fit into memory (or at least, mostly into memory), forget it.
If this all seems like too much, remember that you can just use a filesystem or LVM snapshot online with InnoDB, and then just copy the files. With MyISAM it's a bit trickier but can still be done.
Open another terminal, run mysql, and count the rows in some of the tables in your dump (SELECT COUNT(*) FROM table). Compare to the source database. That'll tell you the progress.
I INSERTed about 80GB of data into MySQL over a network in about 14 hours. They were one-insert-per-row dumps (slow) with a good bit of overhead, inserting on a server with fast disks.
24 hours is possible if the hardware is old enough, or your import is competing with something else for disk IO and memory.
I just went through the experience of restoring a 51.8 Gb database from a 36.8 Gb mysqldump file to create an imdb database. For me the restore which was not done over the network but was done from a file on the native machine took a little under 4 hours.
The machine is a Quad Core Server running Windows Server 2008. People have wondered if there is a way to monitor progress. There actually is. You can watch the restore create the database files by going to the Program Data directory and finding the MYSQL subdirectory and then finding the subdirectory with your database name.
The files are gradually built in the directory and you can watch them build up. No small comfort when you have a production issue and you are wondering if the restore job is hung up or just taking a long time.
To extent my understanding on MySQL.
1) Is going for 64bit help? Do I go with installation or stand alone?
2) If I am going to use 64-bit in MySQL Community Service, will it affect the MySQL Workbench which only available in 32-bit? If yes, in what sense?
3) Does the size of the file affect the speed of MySQL when doing calculation, analysis, and graph? I get a lot of big trouble using Excel in big size.
Please guide.
Note: I am working on excel database (which I found out on this website that it is not a good way to do it) with size of 1.34GB 63 files and growing. I would like to change and continue working in MySQL. I need the database for calculation, analysis and graph.
You are confusing a few concepts. But let me first answer your questions.
1/ 64-bit is more powerful than 32-bit, if your server supports 64-bit. So yes, it should "help".
2/ You can use a 64-bit server with a 32-bit client without any problems. They just communicate with eachother using MySQL-statements, bitsize makes no difference there.
3/ The size of the file (table/row/...) does matter. A lot of small tables can outperform one big table in certain cases, especially with multicore/raid/...
Currently have approximately 2000 simultaneouse connections. We average approximately 425 reads and writes per second. We have a read to write ration of 3:1. All of our tables are myisam. Can we expect better or worse performance when we go from mysql 4.1.22 to 5.0?
There's no way for anyone here to tell you without the schema, queries and test data.
Why not setup a dev environment on 5.0 and testing it out?
The main concern should be that the 5.0 Information Schemas, are a HUGE vulnerability and can be used to very easily gain access to the SQL server from remote locations simply by printing off the schema using injection will let an unwanted viewer, view all of the tables and capitalize off the knowledge to get passwords using the same schema for its columns.
The MySQL source tree includes a set of benchmark tests written as Perl scripts. See The MySQL Benchmark Suite for some information. You can download the source distribution for MySQL 5.0.91 at the archives.
Source distribution of MySQL 4.1 doesn't seem to be easily available anymore. You might have to check it old sources from LaunchPad unless you can find a copy of an old source distribution elsewhere on the internet.
However, the comparison that these benchmarks show is only of general interest. It may be irrelevant to how your application performs. For instance, your usage of the database may not take advantage of some performance improvements in MySQL 5.0, but it may run into some regressions in MySQL 5.0 that were necessary.
The only way to get an answer that is relevant to your application is to try the new software with a test instance of your application, using a sample of data that is a realistic model of the type and volume of data your application typically deals with. As #BenS says, no one on a site like StackOverflow can give an answer specific to your application.
You say in a comment that you're very concerned about performance, but if you don't have an instance of your application and database that you can run tests on, you aren't doing the work necessary to satisfy this concern.
I would strongly suggest moving straight to 5.1.45 with Innodb Support. Percona provides an excellent version with XtraDB that provides a number of performance related improvements. Moving off of your MyISAM tables and onto Innodb will provide a huge performance increase in almost all cases. If you are going to burn the QA/Testing time to move, do a full move now, not a half-way step.