Administrator Guide

Drive Spares
Drive spares are drives that Storage Center reserves to replace a drive when one fails. When a drive fails, Storage Center restripes
the data across the remaining drives using the spare drive as a replacement for the failed drive.
Storage Center designates at least one drive spare for each disk class. For SCv2000 series, SC7020, SC7020F, SC5020, SC5020F,
and SCv3000 storage systems, Storage Center groups drives into groups of no more than 21 drives. Storage Center designates one
drive in each group of drives 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.
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
conguration of the server, data can be written to the volume over iSCSI or Fibre Channel.
The Storage Type and Storage Prole selected when the volume is created determines how a volume behaves. The Storage Type
sets the datapage size and redundancy levels. The Storage Prole determines how Data Progression moves pages on the volume
between tiers and RAID levels.
Storage Types
A Storage Type is a pool of storage with a single datapage size and specied redundancy levels. Storage Center assesses the disks
available in a disk folder and presents the applicable Storage Type options. Once the determination is made, it cannot be changed
without assistance from Dell Technical Support, even when disk types change.
NOTE: SCv2000 series controllers manage Storage Types automatically by assigning each disk class to a new Storage
Type. SSD Storage Types have a 512 K datapage size and HDD Storage Types have a 2 MB datapage size.
Disk Types
The types of disks present in Storage Center dene whether a system is considered Standard or Flash Optimized. This classication
further determines how Data Progression moves data between tiers.
A minimum of six SSDs are required for a Flash Optimized array. When two types of SSDs are present, the array must contain at
least six of each type.
Storage Type
Disk Classes
Standard
Write-intensive SSDs + HDDs
HDDs (7K, 10K, 15K)
Flash Optimized
Write-intensive SSDs
Write-intensive SSDs + Read-intensive SSDs
Write-intensive SSDs + Read-intensive SSDs + HDDs
Datapage Size
By default, data is migrated between tiers and RAID levels in 2 MB blocks. Data can be moved in smaller or larger blocks to meet
specic application requirements. These blocks are referred to as datapages.
2 MB: Default datapage size, this selection is appropriate for most applications.
512 KB: Appropriate for applications with high performance needs, or in environments in which snapshots are taken frequently
under heavy IO. Selecting this size increases overhead and reduces the maximum available space in the Storage Type. Flash
Optimized storage types use 512 KB by default.
4 MB: Appropriate for systems that use a large amount of disk space with infrequent snapshots.
CAUTION: Before changing the datapage setting, contact Dell Technical Support to discuss the impact on
performance and for advice about how to ensure that system resources remain balanced.
Storage Center Overview
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