Installation manual

23 ATTO Technology Inc. ATTO Utilities Installation and Operation Manual
Change RAID group properties
A RAID group has properties that are specific to the
RAID group. The value of each property remains with
the RAID group when it is moved from one computer
to another. Some of the properties can only be
specified during RAID group creation whereas others
may be changed at any time during the life of the RAID
group.
1 Select a RAID group in the Groups panel.
2 Click on Properties in the RAID Management
menu.
3 View or change the current properties.
• SpeedRead specifies the cache policy to be
used during read operations. Once a read
command is given, the SAS/SATA RAID
storage controller retrieves the next set of
sequential data from the RAID group and
caches it in internal memory. If you select
Never, read caching is never performed. If
you select Always, read caching is always
performed. If you select Adaptive, the
default, SpeedRead is enabled or disabled
depending on the sequential patterns
detected in I/O requests.
• Auto-Rebuild controls the replacement of a
faulted drive with any available unallocated
drive. When you click on the Auto-Rebuild
check box and the Accept button, Auto-
Rebuild is enabled. If a drive becomes
faulted, the SAS/SATA RAID storage
controller replaces the drive with an
unallocated drive.
• Rebuild Priority specifies the ratio of
rebuild I/O activity to host I/O activity. A
rebuild priority of Same (default value)
indicates that rebuild I/O and host I/O are
treated equally. A rebuild priority of low
indicates that host I/O is given a higher
priority than rebuild I/O. A rebuild priority of
High indicates that rebuild I/O is given a
higher priority than host I/O.
• Prefetch specifies the number of stripes
that are read when SpeedRead is enabled or
adaptive. The valid values for Prefetch are 0,
1, 2, 3, 4, 5 and 6, and the default value is 1.
This property can only be changed after the
RAID group is created. To access this
property, select the RAID group and view its
properties.
4 Click Accept.
Replacing a faulted drive
If a drive in a RAID group fails, the RAID group’s status
becomes degraded. To return to optimal functionality,
replace the faulted drive using one of the following
mechanisms.
Note
All of these mechanisms start a RAID group
rebuild after the drive is replaced. A RAID
group rebuild may take several hours to
complete. The RAID group is accessible
during rebuild; however, performance may
be impacted, depending on the Rebuild
Priority assigned.
Create a Hot Spare Pool
A faulted drive is automatically replaced if a suitable
disk is available in the Hot Spare Pool. You set up a
Hot Spare Pool with drives reserved until a RAID
group member fails; they are not available when
creating a RAID group. Refer to
Creating a Hot Spare
Pool on page 22.