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Date:      Sat, 26 Jul 2008 20:05:46 +0200
From:      Peter Schuller <peter.schuller@infidyne.com>
To:        freebsd-fs@freebsd.org
Subject:   Asynchronous writing to zvols (ZFS)
Message-ID:  <200807262005.54235.peter.schuller@infidyne.com>

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Hello,

I was finally playing around with iSCSI, having never used it before. For=20
convenience, and also because it may be a future use case for real use, I=20
used zvols for my targets.

I could not get write speed above roughly 1 MB/second even in simple cases=
=20
like dd:ing with an 8 MB block size, with the zvol:s on a 6-disk raidz2. Th=
e=20
individual disk utilization of constituent drives remains small (< 3%).=20
Switching to a memory disk target yielded expected performance=20
characteristics.

I notice that there were confirmed issues with writes to zvol:s:

   http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=3D6496356
   http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=3D6496344

The problem is that I'm not really sure how to translate "snv_59" into=20
something that I can compare with the version of ZFS in FreeBSD. Do the=20
above "bugs" still apply to the ZFS version in FreeBSD, or am I hitting=20
something else?

=2D-=20
/ Peter Schuller

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