istgt now supports command queuing in disk type

Daisuke Aoyama aoyama at
Sun Mar 22 17:31:20 PDT 2009


New release was uploaded in my blog.
The command queuing improves especially sequential read
by MCS(multiple connections per session) round robin.
In my post, I uploaded the screen shots using CrystalDiskMark
which is one of popular benchmark in Japan.

You can download CrystalDiskMark(multilingual) from:

I got the result about 1.5x-3x faster than previous 20090314.
If test data was cached, it reached over 200MB/s.

Known Issue and Limitations:
 o queuing is only supported in single initiator environment.
 o LUN thread might have deadlock when an error has occurred.
 o write command is still slow.
 o timeout may occur when using MCS.
 o single connection may be slower than without queuing.

Here is release 20090323:

The screen shots show difference between QueueDepth 16 and 0
(disabled queuing).

The command queuing is disabled by default.
If you want to use it, please add QueueDepth key in the LogicalUnit
section of your configuration. for example:

  # Queuing 0=disabled, 1-255=enabled with specified depth.
  QueueDepth 16

Daisuke Aoyama

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