Date: Sat, 9 Aug 2008 00:07:15 +0200 From: Peter Schuller <peter.schuller@infidyne.com> To: Pawel Jakub Dawidek <pjd@freebsd.org> Cc: freebsd-fs@freebsd.org Subject: Re: Asynchronous writing to zvols (ZFS) Message-ID: <200808090007.25865.peter.schuller@infidyne.com> In-Reply-To: <20080806185909.GC2580@garage.freebsd.pl> References: <200807262005.54235.peter.schuller@infidyne.com> <200807272026.54907.peter.schuller@infidyne.com> <20080806185909.GC2580@garage.freebsd.pl>
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[zvol write performance less than file-on-zfs]
> Not sure why's that, I spent no time on optimizing ZVOL yet, sorry.
Absolutely, I was not complaining! I just felt it was worth mentioning. It =
was=20
not meant to be negative criticism.
> With the patch above we synchoronize in-memory transactions every 5
> seconds or when queue is full or when we receive BIO_FLUSH.=20
That was my understanding. Sorry, I probably wasn't being clear. I thought=
=20
your original comment ("The problem is that we don't between async and sync=
=20
I/O request on GEOM level") implied that there was some reason one could no=
t=20
trust bio_cmd to be preserved correctly (somehow being downgraded from=20
BIO_FLUSH before it reaches the zvol class). Because if this was the case =
it=20
would make perfect sense under the circumstances to treat all writes as=20
flushes, in order to achieve correct semantics for *actual* flushes.
So my question was meant to confirm that this was not the case, because if =
it=20
were, the patch would mean that *actual* flushes would not get treated as=20
such.
Thanks,
=2D-=20
/ Peter Schuller
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