Areca vs. ZFS performance testing.

[Wes Morgan]

On Sun, 16 Nov 2008, Matt Simerson wrote:

>
> On Nov 16, 2008, at 7:15 PM, Danny Carroll wrote:
>
>> Eirik Øverby wrote:
>>> I have noticed that my 3ware controllers, after updating firmware
>>> recently, have removed the JBOD option entirely, classifying it as
>>> something you wouldn't want to do with that kind of hardware anyway. I
>>> believed then, and even more so now, they are correct.
>> 
>> It kinda depends.  If there were a good 8 or 16+ port SATA card out
>> there that *simply* did SATA with no bells and whistles, then there
>> would be no point buying a Raid adaptor when you want to use things like
>> ZFS.
>> 
>> But there are no such cards available.
>
> Allow me to introduce you to Marvell. The sell the SATA controller used in 
> the Sun thumper (X4500). I've used that same SATA controller under 
> OpenSolaris and FreeBSD. Unfortunately, that controller doesn't use 
> multi-lane cables. When you pack in 3 controllers and 24 disks, it's a 
> cabling disaster.
>
> 	http://freebsd.monkey.org/freebsd-fs/200808/msg00027.html
>
>>> Use the RAID-0 disk trick to be able to utilize the controller cache.
>>> And regarding write-back vs write-through; I believe write-through is
>>> equvivalent to disabling controller write cache, however it WILL cache
>>> the writes in order to respond to future reads of the data being
>>> written. I would guess, but I don't know, that this also goes for
>>> disk-level caches too, though, so it probably doesn't matter.
>> 
>> It is interesting to me that the default setting on the Areca card was
>> to have the disk caches turned on.  I think that is strange because by
>> default you have a situation that can lead to data loss even if you have
>> a battery backup unit.
>
> The Areca cards do NOT have the cache enabled by default. I ordered the 
> optional battery and RAM upgrade for my collection of 1231ML cards. Even with 
> the BBWC, the cache is not enabled by default. I had to go out of my way to 
> enable it, on every single controller.

Are you using these areca cards successfully with large arrays? I found a 
1680i card for a decent price and installed it this weekend, but since 
then I'm seeing the raidz2 pool that it's running hang so frequently that 
I can't even trust using it. The hangs occur in both 7-stable and 
8-current with the new ZFS patch. Same exact settings that have been rock 
solid for me before now don't want to work at all. The drives are just set 
as JBOD -- the controller actually defaulted to this, so I didn't have to 
make any real changes in the BIOS.

Any tips on your setup? Did you have any similar problems?