[Pc_Support] 3Ware Escalade 8000, 9500S and 9550SX -- WAS: Drives, RAID, backups oh my!

[Bryan J. Smith]

Damien McKenna <dmckenna at thelimucompany.com> wrote:
> A few quick questions off the top of my head:
> * What IDE controller do you recommend for a 64bit/33MHz PCI slot?

What storage do you want?

If you just want two (2) redundant drives, a $125 3Ware Escalade
8006-2LP (PCI64/66, slows down to PCI64/33) will do nicely.  I've
been buying them and all of them come with the newer AMCC marketing
-- so they are _always_ the last 7.7.1 firmware (anything 7.3+/2001+
was always very stable for me), so no updates required.  The kernel
has had drivers compatible with that firmware since 2004.

> * What happens in a RAID-1 array if one of the drives dies?

The 3w-xxxx driver will send an alert to the syslog.  The 3w-xxxx
driver will also notify smartd if you're running a recent version
that now has 3w-xxxx support.  If you're running 3dm (or 3dm2, which
works on the 7000+, not just the 9000+), then it will use its alert
mechansims, including an e-mail.

The device is rendered "failed" and the array "degraded."  The system
hardware has _no_idea_ anything is gone.  Because the system _never_
talks to the drive.  _Only_ the 3Ware ASIC talks to the ATA
controller which talks to the drive.  The system only talks to the
3Ware ASIC -- which it thinks is the block device.

> How is it recovered?

If you have a hot spare already declared, the rebuild will be
immediate.  A hot spare requires a spare channel and spare drive
already allocated.

If you don't have a hot spare, it depends on if 3dm[2] is already
running and its settings.  If it doesn't automatically try to use any
available drive, then you'll need to tell it that the new drive is a
hot spare and it will rebuild.

If you don't have 3dm[2] running, then you can launch the CLI to
manually do it.

BTW, if the 3Ware 3dm[2], CLI, etc... detects you've merely put in
the same drive, it will _warn_you_ of this!  It does many things to
prevent you from being stupid.  ;->

Lastly, 3Ware is _not_ FRAID.  You don't use the BIOS setup to manage
disks -- although you typically _do_ for the initial (before you've
installed the OS).  The on-board, 64-bit ASIC doesn't care what
you're in -- 16-bit BIOS setup, 32/64-bit via its management
interfaces in the OS, etc... -- it's firmware is doing everything.

> * Is "Ultrium" the same as LTO?

Yes, it's HP's Brand.  LTO is a multi-vendor standard.  HP inflates
the model numbers to reflect the GB size of a 2.4:1 compression ratio
IIRC.  E.g., Ultrium 960 for 400/800GB LTO-3.

Although note that 2.4:1 isn't atypically either, and with 2.4:1,
you'll get an effective DTR of 196MBps (using an actual DTR of 80MBps
over Ultra160 SCSI).


-- 
Bryan J. Smith   Professional, Technical Annoyance
b.j.smith at ieee.org    http://thebs413.blogspot.com
--------------------------------------------------
I'm a Democrat.  No wait, I'm a Republican.  Hmm,
it seems I'm just whatever someone disagrees with.