The storage snapshot is a new adoption by IT industries in this data center-powered world of virtualization and the cloud. You can add backup, replication, and recovery to that list as well.
A set of reference markers for data at a particular point in time is called a storage snapshot. Storage snapshots are excellent tools for a system administrator to create quick and consistent backups of their databases and applications.
A snapshot is nothing but a “picture” of a filesystem at a point-in-time. This “picture” is not a full copy of the data, but a set of pointers to the data. A snapshot provides the user with accessible copies of data that they can roll back to; just like a detailed table of contents.
Zmanda Recovery Manager (ZRM) for MySQL is an easy-to-use, yet flexible and robust backup and recovery solution for MySQL servers. It streamlines the life of a Database Administrator. To acquire a quiescent, consistent copy of the MySQL database, ZRM for MySQL uses various third party snapshots and storage checkpoint mechanisms, while minimizing application downtime.
Snapshots and storage checkpoints scale well when compared to other backup methods, as they create a regular reproduction of the MySQL database with little impact on MySQL applications and do not increase the backup window as databases grow.
The snapshot and storage checkpoint mechanisms are faster when compared to backups to other media; this reduces the time that database tables must be locked. In the case of the MySQL databases or tables using only transactional storage engines, such as InnoDB, the time when the application is locked is further reduced.
Also, during the taking of snapshots of databases or tables that use non-transactional storage engines, such as MyISAM, ZRM for MySQL flushes the database pages to the disk and obtains a read lock on the database(s) / table(s).
The read lock is held only for a moment. When the database resides on the file systems that support freeze/thaw operations such as XFS, VxFS (Veritas file systems), file system I/O (Input/ Output) is stopped before taking a snapshot.
The "snapshot type" as the full backup method are configured in the Backup How page. Only the licensed snapshots appear in the drop-down box.
Let’s have a look at the list of current industry-leading snapshot technologies:
Linux Logical Volume Manager Snapshots
A snapshot capability built into the Linux Volume Manager (LVM) – the default option on a Linux system.
LVM is a way of virtually partitioning a hard disk space such that it is flexibly allocated to various applications. An increasing number of MySQL installations are utilizing it.
ZRM for MySQL helps backup such installations using snapshots (a feature license is required). It is capable of creating temporary snapshots of the logical volumes and use the snapshot volume to do backups. The benefit of using snapshots is that you need to lock the database tables only while creating a snapshot. Once the backups are completed, the snapshots are removed. Snapshots help to create a consistent copy of the MySQL database as the consistency is ensured prior to taking a snapshot.
File system activity is stopped on file systems such as XFS, VxFS (Veritas file systems) that support freeze/thaw operations, before taking a snapshot.
Snapshot capability built into the ZFS filesystem on Solaris and OpenSolaris
Solaris ZFS filesystem from Sun Microsystem includes snapshot capability, which enables near-instantaneous hot backups and rapid restores.
ZRM for MySQL also includes an optional snapshot plugin that integrates with ZFS to create consistent MySQL full backups. It creates temporary snapshots of the ZFS volumes to perform a full backup. Once the snapshots are enabled, ZRM for MySQL can perform backups without impacting MySQL applications. Regardless of database size, database writes will be blocked only during snapshot creation, which typically takes less than a second.
A feature of the WAFLÂ® (Write Anywhere File Layout) filesystem.
Volume Shadow Copy Service from Microsoft introduced in Windows Server 2003. VSS is also available with Windows XP, Vista, and 2008 Server.
Snapshot capability built into the Veritas File System
During backup runs Symantec Veritas file systems (a.k.a VxFSs) allows two technologies to minimize application downtime:
- Snapshot devices- They mirror the primary storage and allow "freezing" for backup while the original data stays live.
- Storage checkpoints- They use the same filesystem volumes as to the original to only mirror changed data.
Additionally, ZRM for MySQL includes an optional VxFS plugin that integrates with the Veritas File System to leverage native Storage Checkpoint capability.
Snapshot capability on the EMC CLARiiON storage systems
EMC Clariion Storage features EMC SnapView, a snapshot technology that eases near-instantaneous hot backups and rapid restores.
ZRM for MySQL comprises of an optional snapshot plugin that integrates with EMC SnapView to create consistent MySQL full backups. It creates temporary snapshots of the EMC SnapView volumes to perform a full backup. Once the snapshots are enabled, ZRM for MySQL performs backups with minimal impact on MySQL applications. During the snapshot creation database, writes will be blocked, which typically takes less than a second regardless of database size.
A feature is available in the IBM Storage Subsystems (DS8000, DS6000, ESS 800, SAN VC).
EqualLogic Smart Copy
A feature in the Dell EqualLogic PS Series.
Our ZRM for MySQL, a product of Zmanda, uses storage snapshots as one of the technologies to do a quick full backup of the MySQL database. We currently support LVM, ZFS, NetApp, VSS and VxFS Snapshots. We have more to come!
Also, be sure to check out the Points to Include in Your Disaster Recovery Plan