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Re: [Qemu-devel] [RFC] Disk integrity in QEMU
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] [RFC] Disk integrity in QEMU |
Date: |
Tue, 14 Oct 2008 17:43:50 +0200 |
User-agent: |
Thunderbird 2.0.0.16 (X11/20080723) |
Anthony Liguori wrote:
> Avi Kivity wrote:
>> I don't think O_DIRECT should be qemu's default, since anyone using qemu
>> directly is likely a "causal virtualization" user. Management systems
>> like ovirt should definitely default to O_DIRECT (really, they shouldn't
>> even offer caching).
>>
>
> ovirt isn't a good example because the default storage model is
> iSCSI. Since you aren't preserving zero-copy, I doubt that you'll see
> any advantage to using O_DIRECT (I suspect the code paths aren't even
> different).
If you have a hardware iSCSI initiator then O_DIRECT pays off. Even for
a software initiator, the write path could be made zero copy. The read
path doesn't look good though.
--
Do not meddle in the internals of kernels, for they are subtle and quick to
panic.
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, (continued)
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/12
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/12
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/12
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/12
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/12
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/14
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/14
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU,
Avi Kivity <=
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Laurent Vivier, 2008/10/14
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/16
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Izik Eidus, 2008/10/13
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/14
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/12
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Jens Axboe, 2008/10/17
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/19
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Jens Axboe, 2008/10/19
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/19
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Jens Axboe, 2008/10/19