Re: [SLUG] Network Real-Time Hot Filesystem Replication?

[Adrian Chadd <adrian@xxxxxxxxxxxxxxx>]

On Sun, Apr 06, 2008, Amos Shapira wrote:

> I've been using DRBD for a few months now (just in stand-by mode, but been
> following the forums and docs during that time) and all indications are
> that:
> 
> 1. You CAN'T mount a non-cluster-aware file system even read-only on the
> secondary node since the primary will change FS-structs under the feet of
> the read-only node and cause it to crash (because non-cluster-aware
> filesystems assume that they are the only ones who touch that partition).

> 2. You CAN mount read-write on multiple nodes if you use one of the
> cluster-aware filesystems (GFS and OCFS are regularly mentioned, but if you
> find any other cluster-aware file system then it sounds like it will work
> too).

IIRC they assume a single back-end device. Does DRBD give you a journaling
block device which will stall updates until they've been pushed? How will
the FSes tolerate the device IO being possibly milliseconds later than the
master?

> Have you tried this suggestions? From all I read about DRBD this will cause
> all secondary nodes to crash.

I looked into it about a year ago and I couldn't find any simple way of
doing this using free software. There's CODA/AFS as possible solutions but
they still push the notion of master/slave rather than equal peers, which
Chris mentions he needs (ie, constant synchronisation between each member
rather than periodic pushback..)

Chris, try looking at CODA/AFS support?



Adrian