[DRBD-user] DRBD on loopback devices

paddy at panici.net paddy at panici.net
Wed Feb 28 14:14:06 CET 2007

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On Wed, Feb 28, 2007 at 12:53:44AM +0100, Ragnar Kj?rstad wrote:
> The changelog entry for version 0.2 says that it does not work on
> loopback devices, but I see no further mention of this in the manual or
> in the FAQ.
> 
> Is it still the case, or has it been fixed?
> 

On Mon, Feb 05, 2007 at 08:08:18PM +0100, Lars Ellenberg wrote:
>
> drbd on top of a loop device is expected to deadlock sooner or later
> due to resource starvation in the block io path.
>
> you'd hit this sooner with drbd 0.6, or with drbd 0.7 and kernel 2.4.
> you can probably still hit this with the most recent drbd and kernel.
>
> if you don't have much io load, and you do have much free memory, you
> probably could even run this for a long time and never have problems.
> but eventually it will deadlock.
>
> again:
>
> it _may_ work (though I'm not too sure about that),
> if the loop device is block-device-backed.
>
> it _will_ deadlock if the loop device is file-backed,
> due to block io re-entering the file-io path.
>
> --
> : Lars Ellenberg                            Tel +43-1-8178292-0  :
> : LINBIT Information Technologies GmbH      Fax +43-1-8178292-82 :
> : Vivenotgasse 48, A-1120 Vienna/Europe    http://www.linbit.com :

I got this from my mailbox, but you will can archives of the ml on the web.

Regards,
Paddy




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