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

[Jeremy Chadwick]

On Fri, Jan 07, 2011 at 12:29:17PM +1100, Jean-Yves Avenard wrote:
> On 6 January 2011 22:26, Chris Forgeron <cforgeron at acsi.ca> wrote:
> > 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).
> 
> Where do you find those though.
> 
> I've looked and looked and all references I could find was that
> battery-powered RAM card that Sun used in their test setup, but it's
> not publicly available..

DDRdrive:
  http://www.ddrdrive.com/
  http://www.engadget.com/2009/05/05/ddrdrives-ram-based-ssd-is-snappy-costly/

ACard ANS-9010:
  http://techreport.com/articles.x/16255

GC-RAMDISK (i-RAM) products:
  http://us.test.giga-byte.com/Products/Storage/Default.aspx

Be aware these products are absurdly expensive for what they offer (the
cost isn't justified), not to mention in some cases a bottleneck is
imposed by use of a SATA-150 interface.  I'm also not sure if all of
them offer BBU capability.

In some respects you might be better off just buying more RAM for your
system and making md(4) memory disks that are used by L2ARC (cache).
I've mentioned this in the past (specifically "back in the days" when
the ARC piece of ZFS on FreeBSD was causing havok, and asked if one
could work around the complexity by using L2ARC with md(4) drives
instead).

I tried this, but couldn't get rc.d/mdconfig2 to do what I wanted on
startup WRT the aforementioned.

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.               PGP 4BD6C0CB |