[DRBD-user] SAN, drbd, ha, shared disks, ataoe, iscsi, gnbd

Mark Watts m.watts at eris.qinetiq.com
Tue Aug 12 12:27:11 CEST 2008

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

> This exactly what i have now on one of M servers:
> [root at rhclm ~]# lsscsi
> [0:0:0:0]    disk    IET      VIRTUAL-DISK     0     /dev/sda
> [1:0:0:0]    disk    IET      VIRTUAL-DISK     0     /dev/sdb
> [root at rhclm ~]#
> here, sda and sdb are block devices imported via iscsi from computer1 and
> computer2.
> Question: is possible to group sda and sdb using raid1 software in an array
> (/dev/md0) and after that, on top of md0 to create a logical volume and run
> GFS?
> AFAIK THIS DESIGN IS IMPOSSIBLE because raid software on linux is NOT
> CLUTER-AWARE? So, just using iscsi (or gnbd) to export volX is NOT ENOUGH
> because if i am loosing one computerX i am loosing all data on GFS! Right?

RedHat's LVM documentation appears to suggest that you can let LVM do the 
mirroring, and that LVM is cluster-aware (clvmd).
I've certainly used LVM in an RH-CS cluster, and it works pretty well.

Talking that a step further, it _appears_ that you could configure a cLVM 
mirror over those two devices, then run GFS over the top, but I'd really want 
to test that before I believed it, let alone trusted it.


Mark Watts BSc RHCE MBCS
Senior Systems Engineer
QinetiQ Applied Technologies
GPG Key: http://www.linux-corner.info/mwatts.gpg
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