zfs discuss - Feb 2011 - zpool-poolname has 99 threads

After an upgrade of a busy server to Oracle Solaris 10 9/10, I notice
a process called zpool-poolname that has 99 threads.  This seems to be
a limit, as it never goes above that.  It is lower on workstations.
The `zpool'' man page says only:

  Processes
     Each imported pool has an associated process,  named  zpool-
     poolname.  The  threads  in  this process are the pool''s I/O
     processing threads, which handle the compression,  checksum-
     ming,  and other tasks for all I/O associated with the pool.
     This process exists to  provides  visibility  into  the  CPU
     utilization  of the system''s storage pools. The existence of
     this process is an unstable interface.

There are several thousand processes doing ZFS I/O on the busy server.
Could this new process be a limitation in any way?  I''d just like to
rule it out before looking further at I/O performance.

-- 
-Gary Mills-        -Unix Group-        -Computer and Network Services-

The threads associated with the zpool process have special purposes and are
used by the different I/O types of the ZIO pipeline. The number of threads
doesn''t change for workstations or servers. They are fixed values per
ZIO
type. The new process you''re seeing is just exposing the work that has
always been there. Now you can monitor how much CPU is being used by the
underlying ZFS I/O subsystem. If you''re seeing a specific performance
problem feel free to provide more details about the issue.

- George

On Mon, Jan 31, 2011 at 4:54 PM, Gary Mills <mills at cc.umanitoba.ca>
wrote:
> After an upgrade of a busy server to Oracle Solaris 10 9/10, I notice
> a process called zpool-poolname that has 99 threads.  This seems to be
> a limit, as it never goes above that.  It is lower on workstations.
> The `zpool'' man page says only:
>
>  Processes
>     Each imported pool has an associated process,  named  zpool-
>     poolname.  The  threads  in  this process are the pool''s I/O
>     processing threads, which handle the compression,  checksum-
>     ming,  and other tasks for all I/O associated with the pool.
>     This process exists to  provides  visibility  into  the  CPU
>     utilization  of the system''s storage pools. The existence of
>     this process is an unstable interface.
>
> There are several thousand processes doing ZFS I/O on the busy server.
> Could this new process be a limitation in any way?  I''d just like
to
> rule it out before looking further at I/O performance.
>
> --
> -Gary Mills-        -Unix Group-        -Computer and Network Services-
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss at opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
>


-- 
George Wilson

 <http://www.delphix.com>

M: +1.770.853.8523
F: +1.650.494.1676
275 Middlefield Road, Suite 50
Menlo Park, CA 94025
http://www.delphix.com
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