Prev: jumpstart requests wrong file
Next: Panic strings
From: Darren Dunham on 5 Apr 2010 20:06
On Mar 28, 10:01 am, Canuck57 <Canuc...(a)nospam.com> wrote:
> On 26/03/2010 3:33 PM, Ian Collins wrote:
>
> > On 03/27/10 02:55 AM, Michael Laajanen wrote:
> >> Hi,
>
> >> A ZFS vdev should be up to 9 disk I have read, what is the disadvantage
> >> with having 16 disk in one vdev, compared to two vdevs with 8 disk each
> >> all set to raidz2?
>
> > Two important things will suffer:
>
> > Performance: will suck compared to a stripe of smaller vdevs.
>
> > Reliability: you expose your self to a much greater risk or multiple
> > drive failures. Resilver times will also be slower, compounding the risk.
>
> How would risk of drives be an issue?  Say one raidz2 of 16 versus 2 of
> 8 each?

Random read performance is the main reason you don't want to create
large VDEVs.

> I would really hate to think that if one drive failed, it's mirror is
> spread across all others as if so it is inferior to traditional RAID
> 0+1.

I'm not sure why you're comparing Raid 0+1 to large VDEV
configurations.

If you want to create mirror vdevs, then that is very similar to 0+1
and you don't have any problems. But of course you only get 50% of
your disk space for storage.

>  For any mirror to totally fail, it's opposing mirror must also
> fail.  So spreading the risk across 15 other disks...stupid as any 1 in
> 15 can fail and it is dead.  Where as the probablitities of the exact
> opposite is 1/15.

That really doesn't have anything to do with raidz/raidzn
configurations.

--
Darren
First  |  Prev  | 
Pages: 1 2 3
Prev: jumpstart requests wrong file
Next: Panic strings