Re: [Xen-users] Questions on qcow, qcow2 versus LVM

["Matthew Law" <matt@xxxxxxxxxxxxxxxxxx>]

Yes, I've tried the dmsetup solution and that doesn't seem to work for me
and I couldn't get PVGrub to work unless I used kpartx.  Maybe my mistake
but that was what I ended up using to get everything working.

I see so many potential filesystem issues with Linux that I am seriously
considering moving over to opensolaris despite it not being considered
production ready yet.  ZFS brings a lot of features for a small RAM
overhead and some CPU usage, but given that it does what we currently do
with expensive RAID adapters, it might be worth it.

The other thing with OpenSolaris is they seem to be actively developing
xen/xvm at a time when most of the linux distros seem to be dropping it in
favour of kvm.  I don't want kvm.  I want Xen :-)


Regards,

Matt.


On Mon, December 21, 2009 1:04 pm, Thiago Camargo Martins Cordeiro wrote:
> You can "ummount/free" the "not mounted"/busy LVMs LVs with dmsetup!  ;-)
> Anyway, I agree this is sucks!
>
> Are you using kpartx to map the LVs partitioned partitions to your dom0?
> If
> yes, try to not partition (with fdisk) a LV volume... Just use the LVs
> within your domUs as it is...
>
> Cheers!
> Thiago
>
> 2009/12/21 Matthew Law <matt@xxxxxxxxxxxxxxxxxx>
>
>> I've been using lvm under centos to create the backing store for domUs
>> and
>> although the performance seems acceptable it has some shortcomings.  The
>> biggest of which is the LVM bug which prevents me from removing an lv
>> (it
>> says it is still mounted and it definitely isnt).  I thought this was
>> just
>> a centos bug but it appears to be evident in debian and ubuntu too and I
>> really can't afford a reboot of the dom0 everytime I want to remove a
>> logical volume that was once accessed but now isn't!
>>
>> What are people's experiences with using qcow or qcow2 images over LVM
>> volumes?  The reason I chose LVM was for it's ease of management and
>> relative ease with which you can shrink and enlarge a domU filesystem.
>> Can you do this with qcow?  How does it perform on a dom0 with many
>> running domUs (ie. dozens) ?
>>
>>
>> Thanks,
>>
>> Matt.
>>
>>
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>>
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Matthew Law
Director
Penguin Consulting Services Limited
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