[geeks] Impressive...

[Francois Dion]

On Wed, Mar 4, 2009 at 8:43 PM, Nadine Miller <velociraptor at gmail.com> wrote:
> On Mar 4, 2009, at 5:22 PM, Francois Dion wrote:
>>
>> How are you thinking of using the 2.5"? I use 2x 3.5 for the os
>> (bootable zfs) and /opt and other anciliaries, and two mirrors, for 6
>> drives total. I used to have oracle on a clariion but zfs and sata is
>> faster. If I needed more write performance, I'd add a pair of SSD for
>> the ZIL. But even with multiple ATSC HDTV streams recording and
>> playing at the same time I still have plenty of wiggle room without
>> that, so...
>
> I'd like to hear more about that Oracle Clariion issue if you are willing
to
> share, Francois?

This is at home... yeah, I know, I should seek treatment :)

It was an SGI branded Clariion, with Thor controllers and it was
connected to my E5500. When I found a v480 fully loaded for less than
nothing and that running oracle on that (with dual SAS controllers and
a few SATA drives)  was light years faster than the E5500 + clariion,
I decommissioned them. I kept the E5500 because it is in a E5000
"shorty" cabinet and that is where I put the v480, ups etc. Plus if I
ever need a backup SRSS, i'll fire the 5500 back up.

Storage is a complete system, hardware, software and layers. It's hard
to guage a complete system based on 1 component.

>>> If I wanted to add the disks in stages what
>>> would work best from a ZFS point of view? I hate the idea of buying 4
>>> disks
>>> at once, for obvious reasons...
>>
>> Add them 2 at a time, mirrored. Then either append the new mirror to
>> the pool, or create a new pool for the new mirror. Not sure what your
>> application is. But do not use ZFS without redundancy.
>
> Why not RAID5?  Is the performance that dramatically different?  If that's
> the case, I'm going to have to re-think my hardware plans.

Well, he was saying he hates buying 4 disks at once. 2 is kind of a
minimum, so mirror. If I had 8 disks, that would be a different
matter, cost differential is much greater, I'd go for raidz2. Put 4
disks on each controllers. 3+1, 3+1 for 6+2 parity.

At 4 disks, it's a toss between capacity and performance, you'd want
to experiment with your load. I do mostly reads, and I get a better
throughput (you could test with bonnie++). But raidz (i'm assuming you
are not talking raid5 as 1 lun that zfs sees as 1 disk) has some
limitations that I find tips the balance to 2 mirrors instead of a 3+1
raidz, which is what I did.

You have to realize that short of plain mirrors, you cant really grow
properly a raidz or raidz2. You cant reduce the size either. That's
why I suggested adding pools in mirrored pairs, until ZFS can properly
grow/shrink/restripe transparently. Currently you have to backup to
tape recreate your new pool and reload from tape (or other backup).
You can scrub / resilver live so I have good hopes that this feature
will eventually make its way in solaris 10 and be usable live.

Francois