[lvm-devel] [BUG-REPORT] mirror legs in the same PV with --alloc anywhere

[brem belguebli]

Yes, Thanks.

Mirrored-log allocated right on the 2 (or more) PV legs is something
we've been expecting for long now, and I'm sure I'm not the only one
in this case.

We had to hack-build our mirrored disks by layering MD over LVM, which
is not that friendly in terms of integration, MD not being
device-mapper friendly (it may have changed now) and in terms of
debugging it's not always easy.

Hope you'll get it right, that'll make a lot of people life easier.

Brem

2010/4/21 Takahiro Yasui <tyasui at redhat.com>:
> On 04/17/10 05:15, brem belguebli wrote:
>> I think things are not clear about this one, and everyone is confused.
>
> I believe that we agreed on what was our goal through this thread.
>
>> Malahal (from IBM) and you have posted a few weeks ago design proposals
>> and patches to add mirrored log capabilities and also the fact that it
>> could be located on the mirror legs (pv in our cases) by using
>> alloc_anywhere.
>>
>> alloc_anywhere, as described in the man page is to let LVM put the data
>> logical extents where ever it wants (not strict allocation policy) which
>> is, in case a mirror is expected completely a nonsense.
>
> Yes, you are right. We can't expect where logical extents are
> allocated for '--alloc anywhere'
>
>> You may, (this is a suggestion), when lvcreating a mirror with
>> mirrored-log
>> - force strict allocation for the LE's (otherwise it' nonsense)
>> - put the mirrored log leg on each PV
>> - And may be disable alloc anywhare when creating mirrors ?
>
> I think that 'mirrored log' capability is very useful and enhancing
> availability is our next step. It is helpful if users can directly
> build a mirror volume, which has a mirrored log and is built on two
> physical devices and also each physical device contains a mirror
> leg and a mirror log, by a simple command line.
>
> I hope this explanation would be helpful.
>
> Thanks,
> Taka
>
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