[dm-devel] Problem when creating snashots

[Milan Broz]

The MoonSeeker napsal(a):
> Where can I find this patch? I'd like to test it..
> 

Patches are in development quilt queue 
http://www.kernel.org/pub/linux/kernel/people/agk/patches/2.6/editing/

related *testing* patches 
dm-io-*.patch
dm-kcopyd-newio.patch
dm-exception-store-newio.patch

but depends probably on some patches in series file.

Note: there is no patch for new dm-io change in dm-raid1 & dm-log,
do *not* use these patches now if you are using mirror (raid1)
target ! 
(Remaining patches - including raid1 - are waiting in Alasdair's mail...)

Milan
--
mbroz at redhat.com

> Le 27 sept. 06 à 12:36, Milan Broz a écrit :
> 
>> The problem with limited number of snapshots is caused by the using
>> big common mempool in dm-io module.
>> (This can happen even you have a lot of free memory...)
>>
>> There are new dm-io patches which introduce new dm-io interface
>> (using private mempools) and solving this type of snapshot limitation.
>>
>> Patches are currently in review and will probably change a bit,
>> but I hope it will in 2.6.19 kernel.
>>
>> Milan
>>
>> -- 
>> mbroz at redhat.com
>>
>> The MoonSeeker napsal(a):
>>> Yes I really need it. I have to create a virtual network editor for my
>>> diploma project. So I have found many virtual solutions but the bestest
>>> for our project is OpenVZ. Unfortunatly, OpenVZ don't offer the copy on
>>> write with his solution, after many tests, I have found a solution based
>>> on LVM.
>>>
>>> The main idea is to have a Virtual Private Server Core and lot of
>>> Virtual Private Server who are a snapshot of the Virtual Server Core.
>>> Now the problem is the limitation of VLM, I need more than 32 servers
>>> (32 snapshots). Will this limitation incresed in futur futur released of
>>> LVM? Or can we broke this limitation?
>>>
>>> Have you a solution, it's relly urgent for me...
>>>
>>> Thanks you
>>>
>>>
>>> Le 26 sept. 06 à 23:14, Jan Blunck a écrit :
>>>
>>>> On Tue, Sep 26, The MoonSeeker wrote:
>>>>
>>>>> I'd like to create many snaphot of an image but I've got when I
>>>>> attemp to create the 32th snapshot :
>>>>>
>>>>> root at B03:/diplome# lvcreate -s -L150M -n 232 /dev/openvz/vps-core
>>>>>   Rounding up size to full physical extent 152.00 MB
>>>>>   device-mapper: reload ioctl failed: Ne peut allouer de la mémoire
>>>>>   Failed to suspend origin vps-core
>>>>>
>>>>> I don't understand the error..
>>>>
>>>> I'm not a native french speaker (hint!) but I assume you run out of
>>>> memory.
>>>>
>>>> Yes there are limitations to the number of snapshots. For every single
>>>> snapshot we have to allocate memory for copying the chunks to the
>>>> exception
>>>> store.
>>>>
>>>> Do you really need that many snapshots at the same time?