Dell POWERVAULT MD3600F - Manual (Page 61)

Planning: MD3600f Series Storage Array Terms and Concepts 61
• Round robin with subset—The round robin with subset I/O load balance
policy routes I/O requests, in rotation, to each available data path to the
RAID controller module that owns the virtual disks. This policy treats all
paths to the RAID controller module that owns the virtual disk equally for
I/O activity. Paths to the secondary RAID controller module are ignored
until ownership changes. The basic assumption for the round-robin policy
is that the data paths are equal. With mixed host support, the data paths
may have different bandwidths or different data transfer speeds.
• Least queue depth with subset—The least queue depth with subset policy
is also known as the least I/Os or least requests policy. This policy routes
the next I/O request to a data path that has the least outstanding I/O
requests queued. For this policy, an I/O request is simply a command in
the queue. The type of command or the number of blocks that are
associated with the command are not considered. The least queue depth
with subset policy treats large block requests and small block requests
equally. The data path selected is one of the paths in the path group of the
RAID controller module that owns the virtual disk.
• Least path weight with subset (Windows operating systems only)—The
least queue depth with subset policy is also known as the least I/Os or least
requests policy. This policy routes the next I/O request to a data path that
has the least outstanding I/O requests queued. For this policy, an I/O
request is simply a command in the queue. The type of command or the
number of blocks that are associated with the command are not
considered. The least queue depth with subset policy treats large block
requests and small block requests equally. The data path selected is one of
the paths in the path group of the RAID controller module that owns the
virtual disk.
Monitoring MD3600f Series System Performance
You can use the Performance Monitor to select virtual disks and RAID
controller modules to monitor or to change the polling interval. Keep these
guidelines in mind when using the Performance Monitor:
• The Performance Monitor does not dynamically update its display if any
configuration changes occur while the window is open. You must close the
Performance Monitor window and reopen it for the changes to be
displayed.
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