[Linux-cluster] clvm mirroring in rhel5.3

Jure Pečar pegasus at nerv.eu.org
Wed Jan 21 00:00:21 UTC 2009

If I read the release notes for rhel5.3 right, then there's now an option
to have lvm mirrors in a clvm environment.

In a quest to have a horizontally scalable server pool where each machine
both provide its local disks to the pool and mounts the global filesystem
provided by the pool, I was thinking along these lines the other day:

* each machine has a small private root fs and exports the rest of the
disks via the storage block protocol of choice (iscsi/aoe/fcoe)
* each machine mounts exported block devices from all other machines
* while we can't do raid5 in lvm, we should be satisfied with mirroring;
clvm takes care of mirroring between pairs of these network block devices
* clvm also takes care of joining together these mirrors in one volume group
* clvm also takes care of logical volumes, carved out of this volume group
* gfs2 takes care of sharing these logical volumes on a fs level between

This way a failure of a single server should not affect the working of the
whole group, while there'll always be a room for growth both on the cpu/ram
side and on the storage/iops side.


Probably in real world such setup would still have too many bottlenecks to
be useful and too many points of failure to be reliable ... But as I see
many uses of it, I'd like to see something like that work reliably & fast
one day.


Jure Pečar

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