Areca vs. ZFS performance testing.
Matt Simerson
matt at corp.spry.com
Sun Nov 16 22:06:48 PST 2008
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.
Matt
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