Dell PowerVault MD3000 - Manual (Page 97)

Maintaining a Storage Array
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The general form of the command is:
save storageArray performanceStats file="filename"
where file is the name of the file in which you want to save the performance
statistics. You can use any file name your operating system can support. The
default file type is .csv. The performance information is saved as a
comma-delimited file.
Before using the save storageArray performanceStats command, run the set
session performanceMonitorInterval and set session
performanceMonitorIterations commands to specify how often statistics are
collected.
Changing RAID Levels
When creating a disk group, define the RAID level for the virtual disks in that
group. You can later change the RAID level to improve performance or
provide more secure protection for your data. To change the RAID level, run
the following command:
set diskGroup [diskGroupNumber] raidLevel=(0|1|5)
where diskGroupNumber is the number of the disk group for which to
change the RAID level.
Changing Segment Size
When creating a new virtual disk, define the segment size for that virtual
disk. You can later change the segment size to optimize performance. In a
multi-user database or file system storage environment, set your segment size
to minimize the number of physical disks needed to satisfy an I/O request.
Use larger values for the segment size. Using a single physical disk for a single
request leaves other disks available to simultaneously service other requests. If
the virtual disk is in a single-user large I/O environment, performance is
maximized when a single I/O request is serviced with a single data stripe; use
smaller values for the segment size. To change the segment size, run the
following command:
set virtualDisk ([ virtualDiskName ] | < wwid >)
segmentSize= segmentSizeValue