[DRBD-user] Meta device too small in 8.3.2

Lars Ellenberg lars.ellenberg at linbit.com
Sat Jul 18 12:34:40 CEST 2009


On Fri, Jul 17, 2009 at 06:17:35PM +0200, Raoul Bhatia [IPAX] wrote:
> On 17.07.2009 16:51, Gianluca Cecchi wrote:
>> On Fri, Jul 17, 2009 at 4:22 PM, Gianluca
>> Cecchi<gianluca.cecchi at gmail.com>  wrote:
>>> drbd is 8.3.2 and O.S. is F11 x86_64 with kernel 2.6.29.5-191.fc11.x86_64
>>>
>>> I read in previous posts that an external meta device of about 4Mb is
>>> sufficient for about 100Gb od drbd device
>>> (http://lists.linbit.com/pipermail/drbd-user/2009-February/011404.html)
>>>
>>> In my case with 8.3.2 it seems that 8MB are not enough for 52Gb.
>>> I have:
>>
>> Ok, perhaps it was my fault understanding man page.
>> It seems that when you use meta-disk you have to use index and in that
>> case you need at least 256MB????
>
> as far as i recall you need *exactly* 256mb for your meta disk.

get your facts straight.

you need _exactly_ 128 MiB _per_ _index_ .
which, btw, also means that this form of fixed size external meta data
limits usable device size to slightly less than 4TiB.

so if you plan to use /dev/whatever[0] only,
/dev/whatever needs to be at least 128 MiB.
if you plan to use /dev/whatever[0], .... /dev/whatever[15],
then it needs to be at least 16*128 MiB == 2 GiB.

> if /dev/cciss/c0d0p4 is for example 1gb in size, then you can use
> /dev/cciss/c0d0p4[0] throu /dev/cciss/c0d0p4[3] to store 4 drbd
> metadisks

nope, on  1GiB, there is enough room for 8 indexed,
fixed size drbd meta data blocks.

if you want to go for external meta data,
you'd be more flexible with flexible-meta-disk on LVs.

-- 
: Lars Ellenberg                
: LINBIT HA-Solutions GmbH
: DRBD®/HA support and consulting    http://www.linbit.com

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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