Re: PCI Express 2.0 SATA 3 host bus adapter
On 7/11/2013 11:25 AM, Henrique de Moraes Holschuh wrote:
> On Thu, 11 Jul 2013, Stan Hoeppner wrote:
>>> At some point in the future, I may buy one or two additional HDD and use
>>> hardware RAID.
>>
>> It's best to use identical drives with identical firmware, which means
>> buying all your drives up front from the same lot. You also need to
>
> That is a fast way to data loss.
This is FUD, plain and simple.
Henrique you should know better than to make such statements especially
given your @debian.org email address. Some people may think you know
what you're talking about, when you absolutely do not.
> You do not want the drives to fail close
> to each other, so get them from different manufacturing lots, preferably
> with different manufacturing dates separated by at least 6 months.
You're out of your element Henrique. Some who use strictly software md
RAID prefer this strategy, and conceptually it makes sense. However in
the real world, when you order drives, the vendor doesn't allow you to
pick and choose lot numbers, firmware revs, and manufacturing dates.
With respect to hardware RAID controllers, the current discussion you
responded to, having a bunch of drives from different vendors with
different firmware is a recipe for disaster. md RAID can tolerate just
about anything. The firmware on most hardware RAID cards cannot,
because they are designed for speed, not compatibility with any/every
drive combination.
Order a 24 drive FC/SAS RAID chassis from Dell, EMC, HP, IBM, SGI,
Oracle, etc, and you will likely receive 24 identical drives with
identical firmware. And if not, the firmware revs of the drives have
been tested and certified to work together and with the controller.
I've worked with hardware RAID controllers for 15 years now, including
Adaptec, AMI, Mylex, and LSI. LSI absorbed both AMI and Mylex years
ago, starting its RAID product line. The "MegaRAID" brand name came
directly from AMI. I have an old AMI MegaRAID 428 three channel UW SCSI
board manufactured in 1997, retired to a box around here somewhere.
Back to the point, over the years every time I had an issue and called
support at any of the RAID vendors, the first question they asked was
"which RAID card and firmware version?" The seconds question was "how
many drives, which vendor, does the firmware rev on all drives match?
If not, what is the firmware rev on each drive?"
Invariably the problem always boiled down to a firmware mismatch on one
of more of the drives. With some drives the firmware could be flashed
and I was able to fix the problem by flashing them all to the same
firmware rev. In other cases the drives could not be flashed, or even
if they could the vendor preferred I send the drives back and they cross
shipped me matching replacements. Seagate did this a few times, once
cross shipping me $4800 of new drives with factory matched firmware. I
already used mostly Seagate and this level of service put an exclamation
point on it.
Unlike md RAID, hardware RAID controllers in the modern era are designed
for the enterprise. With many, if a drive is flagged as failed its
serial number is logged, and that drive can never be used again on that
controller again, even if the drive still technically works. This is to
prevent accidentally adding a bad drive back into service. So when you
build an array out of mismatched junk and the controller starts kicking
drives due to firmware issues, it gets really expensive really quickly
as you must acquire new drives. Thus, buy matching drives on the
approved compatibility list and avoid these problems. There are vendors
who will sell you enterprise drives with matching firmware. Newegg is
not one of them.
So please, do tell people that they should use drives from different
vendors with mismatched firmware on a real RAID controller, and that if
everything matches they'll lose data. Fifteen+ years of experience
proves the exact opposite of what you say. In reality, drives and
firmware need to match, or be certified by the vendor. If not you'll
drop drives constantly at best, and lose your array at worst once you
put some load on it in production.
--
Stan
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