Request for opinions - gvinum or ccd?

xorquewasp at googlemail.com xorquewasp at googlemail.com
Sat May 30 19:18:44 UTC 2009


On 2009-05-30 14:43:54, Mike Meyer wrote:
> On Sat, 30 May 2009 18:52:39 +0100
> xorquewasp at googlemail.com wrote:
> > Simple question then as the handbook describes both ccd and gvinum -
> > which should I pick?
> 
> My first reaction was "neither", then I realized - you didn't say what
> version of FreeBSD you're running. But if you're running a supported
> version of FreeBSD, that doesn't change my answer.

Sorry, yeah. FreeBSD 7.2-RELEASE on AMD64.

> If you're running 5.3 or later, you probably want gstripe. If you're
> running something older than that, then gvinum won't be available
> either, so you'll need to use ccd. I always figured gvinum was a
> transition tool to help move from vinum to geom, which is why it's
> managed to get to the 7.0 release with some pretty painful bugs in it,
> which don't show up in gstripe.

That sounds like the kind of entertainment I don't particularly want!

> The handbook clearly needs to be rewritten - ccd isn't supported
> anymore, except via the geom ccd class. However, I think zfs is going
> to change it all again, so such a rewrite wont' be useful for very
> long. I don't think zfs supports a two-disk stripe, thought it does do
> JBOD.
> 
> If you're running a 7.X 64-bit system with a couple of GIG of ram,
> expect it to be in service for years without having to reformat the
> disks, and can afford another drive, I'd recommend going to raidz on a
> three-drive system. That will give you close to the size/performance
> of your RAID0 system, but let you lose a disk without losing data. The
> best you can do with zfs on two disks is a mirror, which means write
> throughput will suffer.

Certainly a lot to think about.

The system has 12gb currently, with room to upgrade.  I currently have
two 500gb drives and one 1tb drive. I wanted the setup to be essentially
two drives striped, backed up onto one larger one nightly. I wanted the
large backup drive to be as "isolated" as possible, eg, in the event of
some catastrophic hardware failure, I can remove it and place it in
another machine without a lot of stressful configuration to recover the
data (not possible with a RAID configuration involving all three drives,
as far as I'm aware).

xw


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