2017-02-08 15:27:11 +0100, Max Reitz:
[...]
> A bit of a stupid question, but: How is your performance when using
> detect-zeroes=off?
[...]
I did try that. See:
} Note that passing detect-zeroes=off or detect-zeroes=unmap (with
} discard) doesn't help (even though FALLOC_FL_PUNCH_HOLE is
} suppo
2017-02-08 00:43:18 +0100, Max Reitz:
[...]
> Therefore, the patch as it is makes sense. The fact that said lseek() is
> slow on ZFS is (in my humble opinion) the ZFS driver's problem that
> needs to be fixed there.
[...]
For the record, I've mentioned the qemu performance implication at
https://g
2017-02-08 00:43:18 +0100, Max Reitz:
[...]
> OTOH, it may make sense to offer a way for the user to disable
> lseek(SEEK_{DATA,HOLE}) in our "file" block driver. That way your issue
> would be solved, too, I guess. I'll look into it.
[...]
Thanks Max,
Yes, that would work for me and other users
2017-02-02 16:23:53 +0100, Laszlo Ersek:
[...]
> You didn't mention what qcow2 features you use -- vmstate, snapshots,
> backing files (chains of them), compression?
>
> Since commit 2928abce6d1d only modifies "block/qcow2.c", you could
> switch / convert the images to "raw". "raw" still benefits
Hello,
since qemu-2.7.0, doing synchronised I/O in a VM (tested with
Ubuntu 16.04 amd64 VM) while the disk is backed by a qcow2
file sitting on a ZFS filesystem (zfs on Linux on Debian jessie
(PVE)), the performances are dreadful:
# time dd if=/dev/zero count=1000 of=b oflag=dsync
1000+0 record
For the record, there's more on that bug at
http://thread.gmane.org/gmane.linux.ubuntu.bugs.server/36923
--
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https://bugs.launchpad.net/bugs/595117
Title:
qemu-nbd slow and missing "write
2010-06-24 00:16:03 -, Jamie Lokier:
> Serge Hallyn wrote:
> > The default of qemu-img (of using O_SYNC) is not very sensible
> > because anyway, the client (the kernel) uses caches (write-back),
> > (and "qemu-nbd -d" doesn't flush those by the way). So if for
> > instance qemu-nbd is killed,
2010-06-16 20:36:00 -, Dustin Kirkland:
[...]
> Could you please send that patch to the qemu-devel@ mailing list?
> Thanks!
[...]
Hi Dustin, it looks like qemu-devel is subscribed to bugs in
there, so the bug report is on the list already.
Note that I still consider it as a bug because:
- s
