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Storage setup and configuration
15 Dell EMC SC Series: Microsoft SQL Server Best Practices | CML1057
4.3.5 SSD considerations
The type of files that benefit the most from SSDs varies from environment to environment. Monitor the
performance of the database volumes to determine the best fit for SSDs. If there are not enough SSDs to
function as tier 1 storage for all SC Series volumes, the Storage Profiles for Flash Optimized Storage can be
used to control tiering.
4.4 SC Series snapshots
SC Series snapshots, previously called Replays, are very powerful when combined with SQL Server. By
leveraging snapshots, protecting and recovering databases is very fast and space efficient, even for large
databases.
Dell EMC strongly recommends using Replay Manager to take snapshots of database volumes while SQL
Server is online. Using Replay Manager is the only way to ensure transactional consistency, since writes are
frozen inside of SQL Server while the snapshots are taken. Snapshots of active database volumes taken
without Replay Manager may not be usable for database recovery. Replay Manager also allows snapshots to
be used as the starting point of a restore chain that includes transaction log backups, as databases can be
restored without recovery. In addition, restore points created by Replay Manager are fully logged in SQL
Server providing complete backup integration.
Even though Replay Manager allows specific databases to be selected, snapshots are taken on the entire
volume. If all databases on a given set of volumes are not backed up together, disk space could be wasted on
the array. Consider placing the databases for each backup set on a separate set of volumes.
Placing a large database on its own set of volumes allows additional recovery flexibility when using Replay
Manager. If a database is on its own volumes and in its own backup set, the database can be recovered very
quickly using the Resync method in the Replay Manager Explorer or the Resync-RMRestorePoint
PowerShell cmdlet without affecting other databases. This can be a big time saver when recovering a large
database using a Replay Manager restore point and transaction log backups.
When taking snapshots of database volumes without Replay Manager, it is recommended to use a
consistency group. This will increase the odds of a successful database recovery using those snapshots.
Using a consistency group on the SC Series array allows snapshots to be taken on multiple volumes at the
same point in time. For information on how to setup a consistency group, see the "Managing Snapshot
Profiles" section in the Dell Storage Manager Administrator’s Guide.
Dell EMC recommends taking a snapshot of each user database volume at least once per day, with a
retention period of 25 hours or longer. Data Progression moves frozen pages in the snapshot according to
settings in the storage profile. If the default storage profile Recommended (All Tiers) is used, frozen pages
in the snapshot are moved to RAID 5, while writes will still occur at RAID 10. This allows tier 1 space to be
used more efficiently.
Tasks ideally suited for using snapshots with SQL Server include the following:
• Restoring a copy of a database to quickly recover data or objects after errant updates or deletes
• Restoring a copy of a database on the original server or another server for development, testing or
reporting
• Replicating databases to a DR location (during a DR test, databases can be recovered without
interrupting replication)
• Big data environments where the size of the databases makes frequent backups impractical.