Questions about geom-gate and RAID1/10 and CARP

[Ivan Voras]

Michael Schuh wrote:

> i have searched informations about geom-gate and RAID1 or
> Raid10 over TCP/IP. But nothing relevant found, so that i write
> the questions here.

Actually, there has been some discussion about this, but you probably 
won't like the result...

> Has anyone any experiences with geom-gate and doing RAID1 or RAID10 over
> TCP/IP? And has anyone a good solution in Production use?

Theoretically, yes - it can be done this way. You could use any 
GEOM-aware RAID solution, and throw ggate in the mix.

When I tried it (back in early 5-stable days) I could create the setup 
just fine, but could not stabilise it - gmirror kept loosing the ggate 
component(s), possibly(?) due to timeouts from network latency. IIRC, 
just around the time 6-stable was branched there was a similar report 
from somebody else. BUT, ggate has had several changes since then that 
should address performace, so maybe it's time to try again.

There's another problem: if you do get the over-the-network mirroring to 
work, you won't be able to share data this way: the 
one-writer-multiple-readers scenario won't work because the filesystem 
doesn't support it on the reader side (when the data gets modified by 
the writer, the reader doesn't know about it). Readonly-for-all scenario 
will work.

(see also this: http://docs.freebsd.org/cgi/mid.cgi?438B05D6.3000108 - 
I'll maybe find the time soon)