Hi Doug,
> I have been digging around in archives, etc, but can't decide which
> hardware raid controller will be the best for Linux. The
> options for U160
> multichannel hardware RAID seem to be the Mylex ExtremeRAID
> 2000, the
> Adaptec 3400S, and the AMI MegaRAID (Elite/Enterprise
> 1600).
I'm using the AMI MegaRAID (Elite1600) and the Mylex ExtremeRAID
(ExtremeRAID1100 - the 2000 is quite new so not sure about this one).
These both have mature drivers. Can't say I know about the Adaptec
3400S - can't seem to find much info/experience about running it with
Linux - maybe uses I2O which isn't as mature on Linux??
The AMI I think has a few more benefits IMHO than the Mylex:
* It supports non-disk devices (ie. tape units, SAF-TE processors etc)
(The Mylex supports SAF-TE but doesn't allow access to it from Linux
AFAIK - From Linux's point of view, the Mylex is not a scsi driver,
its a special disk block driver - with no generic SCSI interface)
* AMI supports 64bit/66MHz - the others are 64bit/33MHz
* It has a Linux gui (megamanager) for configuring logical disks (the
mylex requires you to reboot into BIOS AFAIK)
* It is a scsi device rather than a proprietary block device (like the
Mylex DAC960) meaning you can take advantage of more generic scsi
infrastructure such as 'echo 'scsi add-single-device 1 0 1 0 >
/proc/scsi/scsi' for dynamically adding disk devices (although DAC960
driver does have some pretty neat /proc/ filesystem stuff for
monitoring/starting rebuilds etc)
I'm using both of these for shared-scsi clustering - both of them
support multi-initiator clustering so you can have two hosts talking
to the same disks. I'm still testing the AMI but my Mylex in
production has been running seamlessly on a shared-SCSI bus for over
6months.
Both the AMI and Mylexs required firmware upgrades to get it to work
with my disks but after this - it seems to be working like a dream
(out of the box RH6.2 detects AMI or DAC and works fine - i'm now
using megaraid driver in 2.4.3 and has been okay with my testing so
far).
Funny thing is though - I get better performance using Software-RAID
on 2.2 kernels using a non RAID adaptec 7899 than with either of these
RAID controllers. Unfortunately I can't use Software RAID in a
clustered environment and hardware RAID makes me feel a lot more
comfortable.
> I won't have
> time for constant tinkering, so mature hassle-free drivers
> and support
> software is probably my number one concern.... any hints
> for me? The
> motherboard supports 64bit/66MHz PCI, btw.
>
> And, from the what-a-newbie column, maybe someone can help
> me out here:
> If I buy 3 HDs now, and put them together in a RAID5, can I
> simply add 3
> more drives later on? I don't neccesarily want to resize
> the existing
> partitions, but rather to be able to add new ones within
> the RAID. It
> seems like this would be a common thing, but I seem to
> recall an email
> saying this is problematic.
No worries, just add another logical disk using the 3 new drives -
will appear as another SCSI device. It should be possible to do this
without a reboot with the AMI (although haven't tried this yet) if you
have a hot-swapable drive cabinet.
~mc
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