ZFS: root pool considerations, multiple pools on the same disk

[Nikolay Denev]

On Dec 19, 2011, at 2:46 PM, Hugo Silva wrote:

> Hello,
> 
> I've been doing some tests with 9.0 RC3 and ZFS. This particular server
> has 6 disks and a single zpool on mfid?p3 partitions, which I've
> temporarily arranged into a raid-10 with 2 spares, single pool.
> 
> 
> I've been thinking about whether it makes sense to separate the rpool
> from the data pool(s)..
> 
> It seems to make sense at some levels to separate the rpool from the
> app/user data, but to me it's less clear whether this is a good idea or
> not when the backing disks are all the same.
> 
> One idea would be creating a 4-way mirror on small partitions for the
> rpool (sturdier), and a zfs raid-10 on the remaining larger partition.
> 
> I'm curious about the performance implications (if any) of having >1
> zpools on the same disks (considering that during normal usage, it'll be
> the data pool seeing 99.999% of the action) and whether anyone has
> thought the same and/or applied this concept in production.
> 
> Regards,
> 
> Hugo

Hello,

It depends on what you will run on the machine but keep in mind that
the root pool is limited to a single vdev and you cannot add ZIL/LOG devices to 
the root pool.
As for the performance, I don't think it will make a difference having separate root and
data pools, except that you will have less spindles for the data pool.

Regards,
Nikolay