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BP1014 Enhancing SQL Server Protection using Dell EqualLogic Snapshot Smart Copies
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Restoration Tools and Processes The tools and processes your enterprise has in place to restore
data ultimately determine what kind RTOs you are able to support. Some tools
may require multiple manual steps in order to complete the restore process. A
long and complicated recovery process can increase the chances for human
error. The number different teams involved in data recovery can also impact
restoration times.
2.1 Using Snapshots
In general, a snapshot preserves a point-in-time copy at the time the snapshot function is invoked.
Snapshots can complement your backup strategy by helping you improve your achievable RPO and
RTO goals. The snapshot can be used to facilitate point-in-time roll-back of a database. It can also be
placed on-line so that you can recover data from it. A backup application can also utilize the snapshot
as a source from which you create backups.
SQL Server® 2008 includes a native snapshot feature that database administrators can use to copy
and retain the state of database at a particular time. Snapshots are also available at the storage layer.
Using the storage vendor provided snapshot tools database administrators can take SQL Server®
snapshots and keep point in time database copies on the SAN.
Though snapshots can be very helpful to improve overall SQL protection strategy, careful
consideration must be paid when selecting the snapshot functionality to protect your SQL Server®
environment. In SQL Server® environments, snapshots should have the following characteristics:
Application Consistency In a SQL Server® environment snapshots need to be able to create
transactionally consistent point-in-time copies. If the snapshots are not consistent then
you will not be able to perform a successful or complete recovery of the database from
the snapshot. To meet this requirement, the system creating the snapshot must work in
concert with SQL Server® to quiesce database activity when creating the snapshot.
Execution Speed To protect critical applications without compromising on performance and
uptime, it is important that the protection tools take minimal time to create a consistent
point in time copy of the data. Database snapshots creation time should be as short as
possible.
Performance Impact Not all snapshots are created and maintained in the same way. For
instance, due to the way that native snapshots are implemented in SQL Server®,
increasing the number of snapshots retained over a period of time can have a negative
impact on system performance. Ideally, snapshot functionality should have minimal
impact on the application performance even if multiple snapshots are created and
retained.
Easy Restoration You should be able to easily recover data from the snapshot, or restore the
system to the point when the snapshot was created. The process should not be time
consuming, and should allow you to accomplish a complete or partial recovery faster
than if you used just backups and recovery logs.