[DRBD-user] primary/primary drbd + md + lvm

Michael Tokarev mjt at tls.msk.ru
Thu Sep 17 23:42:18 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.


Gianluca Cecchi wrote:
[]
> And what about instead do somthing like this:
> 
> - sda and sdb on both nodes
> - raid0 on both nodes so that on eac node you have one md0 device
> - only one drbd resource based on md0 on both

This is wrong.  If either disk fails, whole raid0 fails,
ie, half the thing fails.

With reverse approach, ie, two drbd resources on top of
disks, and raid0 on top of drbd resources - if any disk
fails only that 1/4 of whole thing fails.

It's classical raid10.  It's always done like
disk => mirroring => striping, but never like
disk => striping => mirroring.

> - use drbd0 device as PV for your VG
> - add clvmd to your cluster layer (you need cman too for clvmd)
> 
> I'm doing it but only with one disk per node

With one disk per node it's simple raid1.

/mjt



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