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Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation
From: |
Max Reitz |
Subject: |
Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation |
Date: |
Mon, 10 Apr 2017 17:03:06 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 |
On 10.04.2017 10:42, Kevin Wolf wrote:
> Am 07.04.2017 um 19:10 hat Max Reitz geschrieben:
>> One case I'd be especially interested in are of course 4 kB subclusters
>> for 64 kB clusters (because 4 kB is a usual page size and can be
>> configured to be the block size of a guest device; and because 64 kB
>> simply is the standard cluster size of qcow2 images nowadays[1]...).
>
> Why should the current default cluster size be an argument for anything?
> 64k is a tradeoff between small COW size and large allocation
> granularity that seemed to work well (and it used to be the maximum
> cluster size originally, so it seemed safer than 128k).
>
> With subclusters, we have a completely different situation and need to
> find a new default that works best. I'm relatively sure that 64k are too
> small under the new conditions.
>
> Also, undefined reference: [1] (I was hoping to find a better argument
> there...)
I meant [1] to be basically what you just said.
Well, the thing is that 64 kB is still better than 32 kB. :-P
Max
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- Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation, (continued)
- Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation, Eric Blake, 2017/04/06
- Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation, Stefan Hajnoczi, 2017/04/07
- Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation, Max Reitz, 2017/04/07
- Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation, Kevin Wolf, 2017/04/10
- Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation,
Max Reitz <=
- Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation, Alberto Garcia, 2017/04/11
- Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation, Max Reitz, 2017/04/11
- Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation, Alberto Garcia, 2017/04/11
- Re: [Qemu-devel] [Qemu-block] [RFC] Proposed qcow2 extension: subcluster allocation, Eric Blake, 2017/04/11
- Re: [Qemu-devel] [Qemu-block] [RFC] Proposed qcow2 extension: subcluster allocation, Alberto Garcia, 2017/04/12
- Re: [Qemu-devel] [Qemu-block] [RFC] Proposed qcow2 extension: subcluster allocation, Max Reitz, 2017/04/12
- Re: [Qemu-devel] [Qemu-block] [RFC] Proposed qcow2 extension: subcluster allocation, Alberto Garcia, 2017/04/13
- Re: [Qemu-devel] [Qemu-block] [RFC] Proposed qcow2 extension: subcluster allocation, Kevin Wolf, 2017/04/13
- Re: [Qemu-devel] [Qemu-block] [RFC] Proposed qcow2 extension: subcluster allocation, Alberto Garcia, 2017/04/13
- Re: [Qemu-devel] [RFC] Proposed qcow2 extension: subcluster allocation, Kevin Wolf, 2017/04/11