[CentOS] Serial ATA hardware raid.

Sat Apr 16 04:04:41 UTC 2005
Pasi Pirhonen <upi at iki.fi>


On Fri, Apr 15, 2005 at 09:13:17PM +0200, Harald Finnås wrote:
> centos-bounces at centos.org wrote on 15.04.2005 19:11:09:
> > Does anyone know of any SATA controllers that are well tested for this 
> > sort of usage?
> Just have to mention it while I remember. If you decide on the 3ware 9500s 
> controller, be aware that you HAVE to do some manual tuning. It performs 
> like crap out of the box.

This is as good insertion point as anything else, for what i am going
to say.

3ware is working like a champ, but slowly. The tuning won't make it
magically go over 100MB/s sustained writes. Random I/O sucks (what i've
seen) for any SATA-setup. Even for /dev/mdX. Puny oldish A1000 can beat
those with almoust factor of ten for random I/O, but being limited to
max. 40MB/s transfers by it's interface (UW/HVD).

But what i am going to say is that for my centos devel work (as in my
NFS-server), i just recently moved my 1.6TB raid under /dev/md5 with
HighPoint RocketRaid1820. I don't care that NOT being hardware RAID.
The /dev/mdX beats the 3ware 9500S-8 formerly used hands down when you
do have 'spare CPU cycles to let kernel handle the parity operations'.


should be even cheaper 8-port solution, but those RocketRAIDs are
available on like in every store.

Google reveals that there is souce driver for these Marvel-chips
(mvsata340.zip) like in


That driver isn't exactly GPL, but it has been working quite good past
month or two while i've been on my 'testing pahse' with this.

With that Supermicro board, one doesn't even have annoying BIOS
problems at POST (that damn 128k BIOS init window + order of card
detection etc. problems which won't always result the system you'd like
to have :).

So i am not saying the 3ware isn't good solution, i am just saying that
at least for me there are better solutions which gets me cheaper more
compatible and faster solution. The metadevice is just something one
can toss in to any hardware as it's in kernel. The 3ware needs 3ware
for replacement if RAID5(0) is used. I've told that RAID1 on 3ware is
just hardware mirror and those disks can be used on any controller, but
i have not personally verified it.

Then few words about this '3ware driver'. How i see it, it's just a few
lines wrapping linux SCSI-layer to 3ware firmware and not even doing it
too good. There has been constantly talk about that the 3ware firmware
would be the reason of bad performance for example CentOS-3/ext3 + 3ware.
Noone out of 3ware can do anything about it and it's as it is. With
kernel solution, every line of code is there and anyone can study it
and find the problem if it should exist.

The now used metaformat for devices is just something which is
plug'n'play. I just recently had 'a pack of disk laying around in
random order' which had been 8 disk /dev/md5 and RAID5. Plugged those
in a machine and found out that it was re-sunching the raid before i
logged in and i just tossed those disks in w/o any knowledge about the
previous order as i wasn't even going to preserve it. So the linux
software implementation has grown to be pretty damn good and neat.

But then again. I need to get another cup of coffee to really wake up

my .02 euros

Pasi Pirhonen - upi at iki.fi - http://iki.fi/upi/