Michael wrote:
> Several months ago someone mentioned an implementation of network
> raid where the individual raid partitions are nfs mounts or something
> like that.
>
> I would appreciate the reference again, have and application.
>
> Thanks
> Michael
> [EMAIL PROTECTED]
Michael,
it is called Network Block Device (nbd) and it is included in latest kernels.
I have been playing a bit with that and here are my observations -
using kernel 2.1.131-ac9, raid0145-19981215 and raidtools-19981214
(and call for comments from more competent audience) .
1. nbd runs fine, you can export partition, mount it on other machine,
quite stable, excellent performances (for network).
The only problem I had is that somehow nbd-server doesn't get the right
size for exported device. You have to supply it as a parameter. (?)
2. raid 1 (didn't use other modes) is very stable also, resilient, very good product,
after trying it in various fail situations I have it installed on many (3)
production systems (all root mounted).
I had some quirks with previous versions but latest
is a keeper. Too bad it isn't included in 2.2 kernels.
3. nbd & raid together, work - but not good enough for production -
specially if you are interested in HA system as I am and what raid over
nbd is all about.
Raid1 builds on nbd just fine. However I could not start raid on other machine
after simulated failover (umount, raidstop, stop nbd, start nbd client on other
machine,
raidstart on other machine). Raidstart segfaults immediately.
After some tests I discovered that even on the same machine
I build the raid, if I stop it, shut the nbd down, start nbd again
and try to start raid it somehow finds nbd device smaller as actually is
- and correctly reported by nbd-client. Aha, it helps if I unload
nbd module and load it again - then it works.
This looks like minor nbd <-> raid incompatibility to me.
When resolved it would leave us with great HA capability and I will be
more than happy to test it.
You can learn more about nbd on http://atrey.karlin.mff.cuni.cz/~pavel.
Regards,
Dori Seliskar
P.S. And again I also would like to hear any suggestions that could
help me get the raid/nbd work properly in my case.
