ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks

[Chris Forgeron]

You know, these days I'm not as happy with SSD's for ZIL. I may blog about some of the speed results I've been getting over the last 6mo-1yr that I've been running them with ZFS. I think people should be using hardware RAM drives. You can get old Gigabyte i-RAM drives with 4 gig of memory for the cost of a 60 gig SSD, and it will trounce the SSD for speed. 

I'd put your SSD to L2ARC (cache). 


-----Original Message-----
From: Damien Fleuriot [mailto:ml at my.gd] 
Sent: Thursday, January 06, 2011 5:20 AM
To: Artem Belevich
Cc: Chris Forgeron; freebsd-stable at freebsd.org
Subject: Re: ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks

You both make good points, thanks for the feedback :)

I am more concerned about data protection than performance, so I suppose raidz2 is the best choice I have with such a small scale setup.

Now the question that remains is wether or not to use parts of the OS's ssd for zil, cache, or both ?

---
Fleuriot Damien

On 5 Jan 2011, at 23:12, Artem Belevich <fbsdlist at src.cx> wrote:

> On Wed, Jan 5, 2011 at 1:55 PM, Damien Fleuriot <ml at my.gd> wrote:
>> Well actually...
>> 
>> raidz2:
>> - 7x 1.5 tb = 10.5tb
>> - 2 parity drives
>> 
>> raidz1:
>> - 3x 1.5 tb = 4.5 tb
>> - 4x 1.5 tb = 6 tb , total 10.5tb
>> - 2 parity drives in split thus different raidz1 arrays
>> 
>> So really, in both cases 2 different parity drives and same storage...
> 
> In second case you get better performance, but lose some data
> protection. It's still raidz1 and you can't guarantee functionality in
> all cases of two drives failing. If two drives fail in the same vdev,
> your entire pool will be gone.  Granted, it's better than single-vdev
> raidz1, but it's *not* as good as raidz2.
> 
> --Artem