Administrator Guide
Reserved Spare Drive
Prior to Storage Center version 7.3, a spare drive is used as a replacement for the failed drive. Storage Center designates at least one drive
spare for each disk class. Storage Center groups drives into groups of no more than 21 drives, with one drive in each group designated as a
spare drive. For example, a disk class containing 21 drives will have 20 managed drives and one spare drive. A disk class with 22 drives will
have 20 managed drives and two spare drives. Storage Center designates the one additional drive as a spare drive. Storage Center
designates the largest drives in the disk class as spare drives.
When Storage Center consumes a spare drive, a feature called Drive Spare Rightsizing allows Storage Center to modify the size of a larger
capacity spare drive to match the capacity of the drive being replaced in the tier. After modifying the size of the drive in this manner, it
cannot be modied to its original size. Drive Spare Rightsizing is enabled by default for all controllers running Storage Center version 7.2
beginning with version 7.2.11. It allows Dell Technical Support to dispatch larger capacity drives of the same disk class when the same size
drive is not available, providing faster delivery times.
Data Progression
Storage Center uses Data Progression to move data within a virtualized storage environment. Data Progression moves data between tiers
and drive types, as well as among multiple RAID levels within the same tier, for a constant balance of performance and cost.
How Data Progression Works
Once every 24 hours, Storage Center assesses disk use and moves data to disk space that is more ecient for the data usage. By default,
Data Progression runs each day at 7 PM system time, but the timing of the run can be changed in the Storage Center settings. Data
Progression behavior is determined by the storage prole applied to each volume. Data progression runs until it completes or reaches the
maximum run time.
NOTE
: With SCv2000 series controllers, Data Progression moves data between RAID 10 and RAID 5/6 and restripes RAID, but
does not move data between storage tiers.
Data Progression and Snapshots
Storage Center also uses Data Progression to move snapshots. When a snapshot is created, either as scheduled or manually, the data is
frozen and moved to the tier specied by the storage prole to hold snapshots.
Snapshots can occur as a scheduled event according to the snapshot prole, manually by creating a snapshot, or on demand by Storage
Center to move data o of Tier 1 in a ash-optimized storage type.
Low Space Modes
A Storage Center enters Conservation mode when free space becomes critically low, and enters Emergency mode when the system can no
longer write to the disks because there is not enough free space.
Prior to entering Conservation mode, the Storage Center displays alerts indicating that disk space is running low. The alert reects the
amount of space left, beginning with 10%, before the system stops operating. The alert updates each time the remaining space decreases
by 1%.
Storage Center Overview
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