[NTLUG:Discuss] Best SCSI RAID for Linux

[Bryan J. Smith]

On Tue, 2004-12-07 at 17:00, Stuart Johnston wrote:
> To complement the recent discussion of IDE raid options, I was hoping to 
> get some opinions on the best SCSI RAID controllers for Linux.  Most of 
> my experience has been with aacraid devices with which I have been 
> pretty unimpressed,

Anything LSI Logic.  They do _not_ get into the business of customizing
OEM products -- they sell the same design, OEM and retail.  I loved both
Mylex and Symbios Logic solutions, now owned by LSI, before that for
that very reason.  They also have some _powerful_ XScale (i8033x)
superscalar microcontrollers as their I/O processors of their
intelligent cards.  Do _not_ go for a "cheap" i960 (including i8030x) 
IOP SCSI cards that dominate the marketing -- you're going to limit your
performance to barely over 50MBps.

One thing that is a re-occuring theme with Adaptec and other vendors
with Linux is that they are retail-focused, with a customized OEM
front.  That's fine if you run Windows and the OEM provides drivers for
the customized board.  But I don't know how many times I've seen an OEM
board just _dork_ in Linux, because it's customized very differently
than the retail model.

I live 5 miles from the _major_ Adaptec support center here in Orlando. 
The Adaptec guys are very frank on _not_ using OEM equipment on Linux,
but _pure_ retail products.  And Adaptec still seems to have a support
policy that varies on Linux -- no official support for RAID cards, only
consumer products.  That might have changed since early 2004, but that's
how current that policy was the last time I checked.

The only Adaptec products that work well under Linux, consistently, were
the DPT products -- which _all_ used standard i960 IOPs with the _full_
Intel I2O (Intelligent I/O) specification.  Hence why the "dpt_i2o"
driver works for _all_ former DPT ATA and SCSI RAID products.

> particularly after reading about 3Ware's DiskManager software.

What did you hear bad about 3DM (especially 3DM2, which I've used with
older 3Ware Escalade 7000/8000 cards, even though it's only bundled with
the 9000 series)?

BTW, one thing that nips people in the butt, _regardless_ of
"intelligent" card, its drive, the OS or vendor support, is that they do
not sync'd the driver and firmware.  If the driver and firmware are not
compatible, you can have issues.

I've personally seen 3Ware, Adaptec, LSI and ICP-Vortex cards fail to
catch errors for several seconds due to firmware being out of date when
a newer driver was in the kernel.  If you have a firmware that is not
sending codes the driver expects, then the monitoring software won't
always respond in-time.

The issue isn't ATA v. SCSI, it's the card.  LSI uses the _same_design_
for both their ATA and SCSI XScale cards.  DPT did as well before their
Adaptec acquisition as well.  ATA v. SCSI is just the storage
connection, and SATA is _taking_over_ in this space (so much so that
SerialSCSI is being introduced).  It's the on-board "intelligence" that
you need to focus on.

LSI Logic cards with XScale are my vote if you are totally against
3Ware.


-- 
Bryan J. Smith                                 b.j.smith at ieee.org 
------------------------------------------------------------------ 
Beware of advocates who justify their preference not in terms of
what they like about their "choice," but what they did not like
about another option.  Such advocacy is more hurtful than helpful.