Administrator Guide
Disk Classes
Disks are classied based on their performance characteristics. Each class is shown in a separate folder within the Assigned disk folder.
• Hard Disk Drives (HDDs) – For HDDs, the disk classication describes its spindle speed and can be any of three disk types.
– 7K (RPM)
– 10K (RPM)
– 15K (RPM)
• Solid State Drives (SSDs) – SSDs are dierentiated by read or write optimization.
– Write-intensive (SLC SSD)
– Read-intensive (MLC SSD)
Drive Spares
Drive spares are drives or drive space reserved by the Storage Center to compensate for a failed drive. When a drive fails, Storage Center
restripes the data across the remaining drives.
Distributed Sparing
When updating to Storage Center version 7.3, a banner message prompts you to optimize disks. Clicking the link guides you through the
process of optimizing disks for Distributed Sparing. When disks are optimized, spare disk space is distributed across all drives in a drive
folder and is designated as Spare Space. This allows the system to use all disks in a balanced and optimized manner, and ensures the
fastest recovery time following a disk failure. Distributed Sparing is the default for systems shipping with Storage Center version 7.3.
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.
Volumes
A Storage Center volume is a logical unit of storage that can represent more logical space than is physically available on the Storage Center.
Before data can be written to a volume, it must be mapped to a server, then formatted as a drive. Depending on the conguration of the
server, data can be written to the volume over iSCSI, Fibre Channel, or SAS.
The storage type and storage prole selected when the volume is created determines how a volume behaves. The storage type sets the
datapage size and redundancy levels. The storage prole determines how data progression moves pages on the volume between tiers and
RAID levels.
Storage Center Overview
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