Administrator Guide

Table Of Contents
Creating disk folders
Adding disks to disk folders
Managing disk spares
Disk Folders
A disk folder contains both managed drives and spare disk space. Managed drives are used for data storage. Spare disk space is
held in reserve to automatically replace a drive if a drive fails. By default, the Assigned disk folder is the parent disk folder for all
drives. Drives are further grouped by class in subordinate folders.
Disk Classes
Disks are classified 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 classification describes its spindle speed and can be any of three disk types.
7K (RPM)
10K (RPM)
15K (RPM)
Solid State Drives (SSDs) SSDs are differentiated 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. During disk optimization, a meter displays the progress in the
Disks view. 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 or later.
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 modified 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 Technical Support to dispatch larger capacity drives
of the same disk class when the same size drive is not available, providing faster delivery times.
24
Storage Center Overview