5.6

The Disk Queue Length value is the best initial indicator on whether a logical drive has sufficient
throughput and access speed for the tasks being required. The Disk Queue Length should not typically be
more than twice the number of processors in the system for more than very short periods of time. When
viewing this counter, a logical drive that is also used by the page file might show high queuing due to
insufficient RAM, but the counter can be useful to determine whether disk subsystem resources are
appropriate and whether the resources are optimally arranged, such as disks per channel, RAID type, and
so on.
Use SQLIO to Determine IO Channel Throughput
SQLIO is a tool that determines the I/O capacity of a SQL configuration. To predict how well VCM will
function on a particular IO configuration and to obtain a baseline of how well the IO subsystem functions,
run SQLIO before you install VCM.
After you download and install SQLIO, configure the following SQLIO settings to ensure an accurate
report of IO throughput.
n
64K Block Size
n
4 Threads
n
2GB File Size minimum
n
Sequential IO
When you execute SQLIO, verify that you create baseline information for each IO channel (logical disk) to
be used for VCM data, as well as testing both read and write operations.
Configuring SQL Server for VCM
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