Administrator Guide

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

configuration of the server, data can be written to the volume over iSCSI or Fibre Channel.

The Storage Type and Storage Profile selected when the volume is created determines how a volume behaves. The Storage Type

sets the datapage size and redundancy levels. The Storage Profile 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 specified 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 define whether a system is considered Standard or Flash Optimized. This classification

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

specific 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.

Redundancy

Redundancy levels provide fault tolerance for a disk failure. Redundancy options may be restricted depending on the disk size.

• Non-redundant: Uses RAID 0 in all classes, in all tiers. Data is striped but provides no redundancy. If one disk fails, all data is lost.

Do not use non-redundant storage for a volume unless the data has been backed up elsewhere.

• Single-redundant: Protects against the loss of any one drive. Single-redundant tiers can contain any of the following types of

RAID storage.

– RAID 10 (each disk is mirrored)

Storage Center Overview