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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 19:15:21 +0200 |
User-agent: |
Thunderbird 2.0.0.16 (X11/20080723) |
Jamie Lokier wrote:
> However, should the effect of the guest turning off the IDE disk write
> cache perhaps be identical to the guest issuing IDE cache flush commands
> following every IDE write?
>
> This could mean the host calling fdatasync, or fsync, or using
> O_DSYNC, or O_DIRECT - whatever the host does for IDE flush cache.
>
> What this means _exactly_ for data integrity is outside of qemu's
> control and is a user & host configuration issue. But qemu could
> provide consistency at least.
>
We should completely ignore the guest IDE write cache. It was brought
into life by the deficiencies of IDE which presented the user with an
impossible tradeoff -- you can choose between data loss and horrible
performance. Since modern hardware doesn't require this tradeoff, there
is no reason to force the user to make these choices.
--
Do not meddle in the internals of kernels, for they are subtle and quick to
panic.
- [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/09
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Aurelien Jarno, 2008/10/10
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/10
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Paul Brook, 2008/10/10
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/10
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Paul Brook, 2008/10/10
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/10
- 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