Raid + zfs performace.

[Peter Ankerstål]

On 30 okt 2010, at 19.39, Sean wrote:

>> I have a question about raid and zfs. I Have a hardware-raid running.
>> A mirror thats the only storage in my zfs pool. Im going to
>> add another mirror to the machine and my question is, what is the best option performace-wise?
> 
> The best performance option is to get rid of the hardware-raid, and
> present each disc to ZFS in a JBOD fashion.

Ok. RIght now thats not an option. I have a da0 device thats a hardware-raid mirror. and it is currently
the only device in the only pool on the machine.

> 
>> Is it to add the other mirror to the same pool or create another separate pool for that mirror?
>> Btw. Today my disk are quite saturated r/w wise.
> 
> RAID functionality only exists within the context of a single pool.
> You don't create a new pool and then try to mirror the two pools. You
> add the storage to an existing pool, unless you have a reason to start
> a new pool. When I already have a mirror, I like to add new mirror
> sets. It's the equivalent of a RAID 10 scenario.

Yes I know.
I thought maybe because the existing pool is kind of r/w saturated it should be better
to create a new independent pool for the new drives. In that way the heavy activity 
would not "spread" to the new drives.

Now you presented me with a third option. So you think I should skip to create
a new hardware-raid mirror and instead use two single drives and add these as
a mirror to the existing pool? How will zfs handle howswap of these drives?
I've seen a few crashes due to ata-detach in other systems.


> 
> -Sean
>