Date: Sat, 26 Jul 2008 22:51:18 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Peter Schuller <peter.schuller@infidyne.com> Cc: freebsd-fs@freebsd.org Subject: Re: Asynchronous writing to zvols (ZFS) Message-ID: <20080726205118.GB1345@garage.freebsd.pl> In-Reply-To: <200807262005.54235.peter.schuller@infidyne.com> References: <200807262005.54235.peter.schuller@infidyne.com>
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--VywGB/WGlW4DM4P8 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sat, Jul 26, 2008 at 08:05:46PM +0200, Peter Schuller wrote: > Hello, >=20 > 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. >=20 > I could not get write speed above roughly 1 MB/second even in simple case= s=20 > like dd:ing with an 8 MB block size, with the zvol:s on a 6-disk raidz2. = The=20 > individual disk utilization of constituent drives remains small (< 3%).= =20 > Switching to a memory disk target yielded expected performance=20 > characteristics. >=20 > I notice that there were confirmed issues with writes to zvol:s: >=20 > http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=3D6496356 > http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=3D6496344 >=20 > 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? The problem is that we don't between async and sync I/O request on GEOM level, that's why I decided to commit a ZIL log after each write, which wasn't very smart it seems. This is handled differently in version I've in perforce. Could you try the below patch and see how it performs now? http://people.freebsd.org/~pjd/patches/zvol.c.patch --=20 Pawel Jakub Dawidek http://www.wheel.pl pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! --VywGB/WGlW4DM4P8 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4 (FreeBSD) iD8DBQFIi45GForvXbEpPzQRAizYAJ9CBIcCWCJpTeOkBiqNTLAGJX+CggCfd9nx rePeFIxubC3Hou73zMatFnU= =HOCB -----END PGP SIGNATURE----- --VywGB/WGlW4DM4P8--
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