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BP1014 Enhancing SQL Server Protection using Dell EqualLogic Snapshot Smart Copies
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Carefully assess your RPO goals:
Depending on your target RPO goals, you should ascertain whether you can fulfill them with just
Smart Copies alone or would need a combination of backup sets in conjunction with Smart
Copies. For example, consider the following case:
 You cannot tolerate a data loss period of more than 15 minutes
 The size of your SAN volumes combined with the data change rate limits you to creating
one snapshot per hour with a maximum snapshot history of four before you have to delete
the oldest Smart Copy snapshot.
 You run multiple backup schedules against the same database: regular full backups once
per day, Smart Copy snapshots once per hour, transaction log backups every 15 minutes,
and off-host differential backups once every four hours.
In a recovery scenario, you could revert back to the closest Smart Copy (if the data loss occurred
within 4 hours of starting the recovery process and then apply the transaction log backups to roll
the database forward to the point of data loss. This way you will restore much quicker than if you
used backup sets only.
Consider other methods to meet aggressive RTO/RPO goals:
If you have very aggressive RTO and RPO goals that cannot be met with recovery from a backup
set or a combination of backup set recovery and ASM/ME Smart Copies, then you will need to
consider other options: failover clustering, database mirroring, log shipping, or data replication.
Understand the difference between regular EqualLogic volume snapshots and ASM/ME Smart
Copies:
You can also create a snapshot of a volume using EqualLogic group management functions
directly. If you create a snapshot of a volume hosting an active SQL Server® database instance
using this method, then the resulting snapshot will not provide the same level of data consistency
that an ASM/ME Smart Copy snapshot does. Group level snapshots can still be considered “crash
consistent”. Database activity is not quiesced before the snapshot is created, therefore there is no
guarantee that the snapshot will support a clean recovery the way ASM/ME Smart Copy snapshots
can.
4.2 Best Practices: Auto-Snapshot Manager/Microsoft Edition
Auto-Snapshot Manager utilizes EqualLogic volume snapshot features. You should follow the best
practices best practices in this section when using ASM/ME.
Planning snapshot reserve for ASM Smart Copies
 Monitor snapshot reserve space utilization. If the snapshot reserve fills up, then you will need
to either increase the snapshot reserve allocation for the SQL data volumes or delete older
snapshots to free up reserve space.
 If you are not sure how to set the size of snapshot reserve for SQL Server® data volumes, then
you could start by using the default reserve allocation for the volume. To determine if the
reserve size is set optimally you can create a series of snapshots while the system is under load
and monitor how quickly the reserve space is consumed by write activity.