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Chapter 6 RAID Group Management
6.2 Functions in the Action Area for RAID Group
ETERNUS Web GUI User’s Guide
Copyright 2013 FUJITSU LIMITED P2X0-1090-10ENZ0
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The procedure to change the RAID group parameters is as follows:
Procedure
1 Select which RAID groups to change the RAID group parameters for (multiple selections can
be made) and click [Modify RAID Group Parameters] in [Action].
2 Specify the RAID group parameters, and click the [Modify] button.
• DCMF
Specify the DCMF between 1 - 10. The default value is "1". It is not necessary to change the default
setting for normal use.
The maximum number of commands issued to a drive is changed to a multiple represented by the
specified value. (If "DCMF" is "2", the number of commands is doubled. If "DCMF" is "3", the number
of commands is tripled.) When not changing the DCMF, select "No Change".
The higher the DCMF value is, the more drive throughput is available, improving sequential
performance. Note that high DCMF value may result in a high load on the drive, decreasing
performance.
• Rebuild Priority
Specify the rebuild priority. The default setting is "Low". It is not necessary to change the default set-
ting for normal use.
When not changing the rebuild priority, select "No Change".
When host access is not performed, rebuild, copyback, and redundant copy to RAID groups that is
not registered as REC Disk Buffers are performed with "High" priority regardless of the "Rebuild
Priority" setting.
Rebuild, copyback, and redundant copy performance may be improved by specifying a larger
"Rebuild Priority" value. Note that specifying larger "Rebuild Priority" may cause the degradation of
RAID group performance when performing rebuild, copyback, or redundant copy is performed in the
target RAID group.
• When the "Rebuild Priority" setting is changed, the priority is changed not only for a rebuild, copyback,
and redundant copy that will be performed after the setting is changed, but also for any rebuild,
copyback, and redundant copy operations that are currently being performed.
• When the target RAID group is registered as an REC Disk Buffer, do not select "High" for the "Rebuild
Priority" setting. Even if "High" is selected, rebuilding, copyback, and redundant copy are performed with
"Middle" priority during host access.
• Specify the same RAID group parameters for all of the RAID groups that configure a WSV. If different RAID
group parameters are specified, the host access performance may be reduced.
• When specifying the "Throttle " or "Ordered Cut", enable the "Disk Tuning Parameter Setting" in advance.
• RAID groups that configure a WSV can be checked in the [Volume Detail] screen ([WSV Concatenation]
Tab). Refer to "5.1.14 Volume Detail (WSV Concatenation)" (page 93)
for details.