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Date: Wed, 04 Feb 2015 13:54:19 +0900
From: Teruaki Ishizaki <ishizaki.teruaki@lab.ntt.co.jp>
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Subject: Re: [Qemu-devel] [PATCH v4] sheepdog: selectable object size support
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To: Liu Yuan <namei.unix@gmail.com>
Cc: kwolf@redhat.com, mitake.hitoshi@lab.ntt.co.jp, sheepdog@lists.wpkg.org, qemu-devel@nongnu.org, stefanha@redhat.com

(2015/02/02 15:52), Liu Yuan wrote:
> On Tue, Jan 27, 2015 at 05:35:27PM +0900, Teruaki Ishizaki wrote:
>> Previously, qemu block driver of sheepdog used hard-coded VDI object size.
>> This patch enables users to handle "block_size_shift" value for
>> calculating VDI object size.
>>
>> When you start qemu, you don't need to specify additional command option.
>>
>> But when you create the VDI which doesn't have default object size
>> with qemu-img command, you specify block_size_shift option.
>>
>> If you want to create a VDI of 8MB(1 << 23) object size,
>> you need to specify following command option.
>>
>>   # qemu-img create -o block_size_shift=23 sheepdog:test1 100M
>
> Is it possible to make this option more user friendly? such as
>
>   $ qemu-img create -o object_size=8M sheepdog:test 1G

At first, I thought that the object_size was user friendly.
But, Sheepdog has already the value of block_size_shift
in the inode layout that means like object_size.

'object_size' doesn't always fit right in 'block_size_shift'.
On the other hands, 'block_size_shift' always fit right in
'object_size'.

I think that existing layout shouldn't be changed easily and
it seems that it is difficult for users to specify
the object_size value that fit right in 'block_size_shift'.

Thanks,
Teruaki Ishizaki