Selecting raid stripe width – Dell Compellent Series 40 User Manual
Page 238
230
Storage Center 5.5 System Manager User Guide
System Management
Selecting RAID Stripe Width
The default stripe width for storage profiles is 10 wide (RAID 6-10). Modifying this value
updates the RAID 6 selections for all system Storage Profiles. It also modifies the RAID 6
selections for user-created Storage Profiles unless Manual Storage Mode is enabled.
In a standard Storage Center system, a percentage of most-used data is storage on
RAID 10 (striped and mirrored). Data that is used less is stored on RAID 6-10 (which uses
an algorithm to rebuild data if one drive in the logical unit should fail). For RAID 5, the stripe
width determines whether the logical unit is comprised of five or nine drives. For RAID 6,
the stripe width determines whether the logical unit is comprised of six or ten drives.
Distributing data across more drives is marginally more efficient, but increases vulnerability.
Distributing data across fewer drives is less efficient, but marginally decreases vulnerability.
To select RAID stripe width
1 From the Storage Management menu, select System > Properties.
2 Click the Storage tab. The system Storage Properties window appears.
•
For RAID 5, choose between RAID 5-5, which distributes parity across five drives,
or RAID 5-9, which distributes parity across nine drives.
•
For RAID 6, choose between RAID 6-6, which distributes parity across six drives, or
RAID 6-10, which distributes parity across 10 drives.
Figure 189. System Properties – Storage
Caution:
Do not change the system-wide RAID level if the system is in Conservation Mode.
Although it would seem logical that changing the RAID level from fewer drives to
more drives would free space, the system needs additional space to park data