[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [RFC] Disk integrity in QEMU
From: |
Aurelien Jarno |
Subject: |
Re: [Qemu-devel] [RFC] Disk integrity in QEMU |
Date: |
Fri, 10 Oct 2008 17:48:55 +0200 |
User-agent: |
Mutt/1.5.18 (2008-05-17) |
On Fri, Oct 10, 2008 at 07:26:00AM -0500, Anthony Liguori wrote:
> Aurelien Jarno wrote:
>> On Thu, Oct 09, 2008 at 12:00:41PM -0500, Anthony Liguori wrote:
>>
>> [snip]
>>
>>
>>> So to summarize, I think we should enable O_DSYNC by default to
>>> ensure that guest data integrity is not dependent on the host OS,
>>> and that practically speaking, cache=off is only useful for very
>>> specialized circumstances. Part of the patch I'll follow up with
>>> includes changes to the man page to document all of this for users.
>>>
>>> Thoughts?
>>>
>>>
>>
>> While I agree O_DSYNC should be the defaults, I wonder if we should keep
>> the current behaviour available for those who want it. We can imagine
>> the following options:
>> cache=off O_DIRECT
>> cache=read O_DSYNC (default)
>>
>
> Or maybe cache=off, cache=on, cache=wb. So that the default was
> cache=on which is write-through, or the user can choose write-back
> caching.
>
> But that said, I'm concerned that this is far too confusing for users.
> I don't think anyone is relying on disk write performance when in
> write-back mode simply because the guest already has a page cache so
> writes are already being completed instantaneously from the
> application's perspective.
>
Some of my setups rely on host cache. I am using a swap partition for
some guests in order to increase the available "memory" (some platforms
in qemu are limited to 256MB of RAM), and it that case I don't care
about data integrity
--
.''`. Aurelien Jarno | GPG: 1024D/F1BCDB73
: :' : Debian developer | Electrical Engineer
`. `' address@hidden | address@hidden
`- people.debian.org/~aurel32 | www.aurel32.net
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU, (continued)
- 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
- Re: [Qemu-devel] [RFC] Disk integrity in QEMU,
Aurelien Jarno <=
Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Avi Kivity, 2008/10/10
Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Anthony Liguori, 2008/10/10
Re: [Qemu-devel] [RFC] Disk integrity in QEMU, Mark Wagner, 2008/10/11