[Linux-cluster] Mirroring GFS

[Andrea Manca]

Hi to all.

I've a couple of question about interaction between MD devices (software
RAID), GNBD, and GFS.

I'm testing a cluster with four nodes: two gfs and two gnbd nodes.
GNBD1 and GNBD2 export each one a partition over the LAN;
GFS1 and GFS2 import that exported block devices.

I'm interested in mirroring the information in GNBD1 over GNBD2, so i've
thought about creating a md device composed by

/dev/gnbd/GNBD1_PRIMARY
/dev/gnbd/GNBD2_MIRROR

in RAID1 configuration and gfs formatted.
It seem's a reasonable configuration for me, but in:

https://www.redhat.com/archives/linux-cluster/2004-October/msg00055.html

a similar solution (except for a RAID5 configuration), is discussed and
marked as impossible, because Software Raid in linux isn't cluster
aware. This could lead an inconsistency in parity blocks which aren't
locked correctly.
In my opinion two mirrored disks doesn't need a block level locking,
because parity block aren't present.

i've tried this on 4 VMWare machines and it seem work well if you write
(or read) something from GFSx nodes.

Could my solution get working or there is a similar issue applicable in
my situation?
In this second case, are any workarounds possible?


I really appreciate any comment or explanation.

Thank you all in advance.


Andrea.
manca at link.it