[DRBD-user] DRBD and LVM Snapshots on Secondary

Hany Fahim hany at vmdevlabs.com
Thu Aug 13 17:03:17 CEST 2009

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

Hey Jurgen,
Your idea of using LVM both above and below DRBD is interesting. Do you have
any experience with this? Do you know if there is any major performance
penalty for running 2 LVM layers?


On Thu, Aug 13, 2009 at 7:34 AM, Jürgen Scholz <juergen at kernkraft400.com>wrote:

> Hello!
>  But I'm trying to achieve the same thing, and I'm wondering if this is at
>> all possible since this was posted back in 2004. I have a 2-node setup in
>> Primary-Secondary mode. LVM2 sits on top of DRBD. Now due to the enormous
>> performance penalty incurred when taking an LVM snapshot of an active LV, I
>> was wondering if it's possible to take the snapshot on the secondary node
>> only for backup purposes, while leaving the primary untouched. I wouldn't
>> care about the performance hit to the secondary, I'm only concerned with the
>> data being "consistent", and not necessarily "clean".
> If I understand correctly you want to change the contents of the drbd
> resource on the secondary. You will not be able to do that without dual
> primary and clvm.
> You perhaps could use
>   Storage <-> LVM <-> DRBD <-> LVM <-> LVs
> and do the snapshot for the backup on the lower lvm.
> You could disconnect your secondary, promote it to primary, do the backup,
> outdate and reconnect. - But you would lose your consistency this way.
> hth
>  juergen
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