Asynchronous writing to zvols (ZFS)

[Thomas Hurst]

* Peter Schuller (peter.schuller at infidyne.com) wrote:

> I notice that there were confirmed issues with writes to zvol:s:
> 
>    http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6496356
>    http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6496344
> 
> The problem is that I'm not really sure how to translate "snv_59" into
> something that I can compare with the version of ZFS in FreeBSD. Do
> the above "bugs" still apply to the ZFS version in FreeBSD, or am I
> hitting something else?

  WARNING: ZFS is considered to be an experimental feature in FreeBSD.
  ZFS filesystem version 6

http://opensolaris.org/os/community/zfs/version/6/

  This feature is available in:
  Solaris Nevada Build 62

However, some of this looks faimilar from recent Perforce activity:

  This means that zvol needs to support this special command
  (DKIOCFLUSHWRITECACHE), and that it should save zil_commit() for only
  the times it's necessary.

http://perforce.freebsd.org/changeList.cgi?CMD=changes&FSPC=//depot/user/pjd/zfs/...

  Change 145289 2008/07/15 by pjd at pjd_zoo 
  Improve ZVOL performance by only committing ZIL on BIO_FLUSH request,
  not on every BIO_WRITE request.

Which looks like a good candidate.  You could see if ZIL is the problem
by setting vfs.zfs.zil_disable=1

-- 
Thomas 'Freaky' Hurst
    http://hur.st/
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