Is it possible to configure slave in-memory database?
Master db is common, slave for read only operation could suit well into in-memory storage.
If it is not possible with MySQL, what are other database to use such scheme?
It might work for 'simple' slave, such as data size and replication, as well as tolerate lots of limits with the in-memory storage engine.
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I have been reading about MySQL scaling and I found out that MySQL supports two type of architectures :
Master - Slave - Since updates from master to slave are asychronous then it is possible to have incosistent reads in case a slave is not updated ( due to latency or any other reason). So this system is highly available but not very consistent.
NDB Clustering - So MySQL can use NDB engine to deploy a cluster like NoSQL databases where sharding is also involved. I have two doubts in this that let's say I have 3 data nodes then how NDB engine performs JOIN queries because some of data can reside on Node 1 while other can be on Node2. Also does NDB cluster supports replication of data node? And if it supports replication then replication will be done to same data node or any other node?
I want to do synchronous and asynchronous replication, synchronize for some databases, and asynchrony for others.
Asynchronous I am doing it through MariaDB, through the traditional system that has replication.
But I want to implement synchronous replication also with Mysql / MariaDB.
The problem is that I do not know if Mysql Cluster also does that work, or if it is not necessary to have Mysql installed only or MariaDb and only use Mysql Cluster for both.
Thank you.
Disclosure: I am working for the MySQL Cluster team - "MySQL Cluster" as in NDB Cluster.
MySQL NDB Cluster always uses synchronous replication between its nodes. You can still use asynchronous replication to other MySQL instances or MySQL Clusters.
AFAIK only MySQL offers NDB and as open source.
Due to the usual network limitations synchronous replication is better suited for high availability in the local data center. It gives you an always consistent view of your data, two or more active instances and makes programing against it much easier.
Asynchronous is more for replication between data centers or availability zones where you can live with temporary inconsistencies in the data and have your programming model set up accordingly.
"MySQL Cluster" has more than one meaning, so I will avoid it.
"Galera" is the underlying cluster technology in MariaDB, PXC, and (if you do the installation yourself), MySQL.
Galera provides essentially-synchronous among (typically) 3 nodes. Meanwhile, each node can have any number of asynchronous Slaves hanging off it.
Also, one Galera cluster can asynchronously replicate to another such cluster. This is sometimes done with a cluster in each of two datacenters.
Mixing sync and async at the database level is quite unusual, and seems strange. The general principle of Replication is that all servers will have exactly the same (barring delays) data. Please elaborate on what you want to do. Also, think out of the box when it comes to topologies.
There are multiple ways to take a MySQL replication, or rebuilding it. How can we build master-slave replications via LVM snapshot?
And also which is the most effective way among below 4 choices & why ??
Setting up MySQL Replication using mysqldump.
Setting up MySQL Replication using Percona XtraBackup.
Setting up MySQL Replication using Rsync.
setting up MySQL Master-Slave Replication with LVM snapshots.
Since setting up LVM requires major surgery at the filesystem level, that approach could be a challenge. However, once it is done, the rest is relatively painless.
XtraBackup is an improvement on mysqldump.
rsync is good for copying files that are not being modified. When MySQL is running, it is modifying files, and caching unwritten stuff in ram. Sounds sketchy.
I am handling few databases that is growing very fast. Now it is around 12GB and in next few months it will cross 15GB. At this situation I only have the traditional backup process mysqldump running in cronjob. I found significant delay in backup and restore time (hours, even days) for the whole database. Knowing that physical backups are much faster than logical, I found these two, but cannot implement those because of some limitations and company policy.
MySQL Enterprise Backup : which is commercial
Percona XtraBackup : Percona came with this tool specially for Linux environments. And not all companies will agree to use 3rd party tools even though it is open source.
Please suggest any other better backup and restore mechanism for big database specially when the databases are mix of Innodb and MyISAM. Looking for some good suggestions on snapshots
I have personally used Percona XtraBackup toolset. It does some simple procedures to get all the committed data in innodb binlog when it finishes the normal storage. Reading about MySQL Enterprise Backup also can do this.
Incremental backups/snapshots can be made with both Percona XtraBackup and MySQL Enterprise, if that's what you're looking for.
Using a read-only slave, you can maintain separation of the read locks. This will keep your locks from being held on the master read if you backup using mysql free tools.
Another option if you have a slave is you can shut off the slave and rsync the data somewhere for backup.
First I would try using "--single-transaction" with mysqldump as long as all your tables are innodb and you aren't modifying table structure during dump. This will attempt to dump from a single point in time but only when it can be performed without locking your tables.
I haven't tried xtrabackup but it looks like that will do what you want as well.
You could also try setting up mysql replication and dumping from the slave.
Lastly LVM snapshots but that takes a bit more work.
mysql-cluster-expert-5.1 document mentioned that:
"MySQL Cluster tables in MySQL 5.1 are normally stored completely in memory rather than on disk (this is why we refer to MySQL cluster as an in-memory database)"
which means mysql cluster is a distributed memory database, so has anybody ever done a comparison of mysql cluster & redis on speed?
I don't think redis does anything remotely similar to MySQL cluster, so you can't compare them.
MySQL cluster is a high-availability, fuly durable SQL cluster with fully synchronous replication. Redis is not. As far as I understand, redis supports neither synchronous replication, nor SQL.
MySQL cluster means that when you can COMMIT TRANSACTION**, if you lose any cluster member permanently 1ms later, your data are still safe. MySQL cluster query nodes (which are the clients) automatically fail-over in a very short time (typically < 5 seconds).
Redis does absolutely none of this. It is a non-SQL based data store which has master-slave replication (failover? You'd better implement it yourself)
You may as well ask if a motorbike is faster than an ocean liner.
** I don't think redis supports transactions, so that notion is rubbish as well.