Mailinglist Archive: opensuse (818 mails)

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Re: [opensuse] Recover Linux Raid 0 with 2x2port 3Ware Raid 1 cards
On 9/1/2011 12:29 PM, John Andersen wrote:
On 9/1/2011 6:49 AM, LLLActive@xxxxxxx wrote:
I am considering replacing the 2x2 Ports with a 1x4 Port to have a
HW-raid 10 without needing a Linux soft raid, for more safety;

In my humble opinion software raid is much safer than hardware raid if
you are worried about controller failure
or disk failure.

With Software raid:
1) Any compatible controller will do. On the Motherboard, on an add-in
card, in a new machine.
2) You can mix drive types, even drive sizes.
3) You can span controllers. (your current setup kills the raid if one
controller dies)
4) Replacement controllers don't get harder and harder to find as time
goes on

Also, but not related to failure issues
4) Software raid improves as you upgrade the server - its not stuck at
the speed you bought it
5) imposes very little load on the server (contrary to the FUD of the past)
6) easily configured in modern Distros, especially when your machine has
4 or 6 SATA ports. Yast does it.

I've been the 3Ware route. Its nice in that if done correctly your
computer OS need never be aware
that a raid is involved at all. But over the years I have migrated to
software raid for the ease
of maintenance, migration, disk replacement. I've used raid controllers
with their raid software
turned off (via jumpers) just for the ports in the past, but my current
servers have scads of
Sata/eSATA ports making this unnecessary. I still endeavor to put the
drives of an array on
different controllers although I've never seen any measurable difference
in doing so.

Non of this is helpful in your current predicament, just a philosophical
discussion.

+1 all the way.

Used many hardware raid cards over the years on several varieties of unix. It was ok back in the old days when there was no other choice, but since years ago I can't stand the hassle of dealing with hardware raid cards.

When you only have one machine, and only have one card, and it's nowhere near time to migrate or upgrade, a hardware card looks enticing.
It's easy, and moving day is years away and you can afford the time to do a slow full copy to some different new hardware since it's just your one machine and you have nothing else to do and only yourself not a boatload of angry paying customers to worry about.

If you have the luxury of living in a well funded or at least large, and utterly homogeneous, environment "We're an [HP|Dell|Intel|FooXYZ] shop, we have an account with FooXYZ and even though they don't make this FooXYZ card any more and even though it's all proprietary and only fits in this one FooXYZ case, we have piles of'em lying around..." then a hardware raid card looks enticing.

If you're trying to grant the benefits of raid to an OS that can't do it in software, then a hardware raid card looks enticing.

Any other situation and they're great right up until there's a problem and then they're just the reason you're telling the customer or boss any of a dozen different excuses instead of handling the problem without even resorting to backups. Perhaps after some googling and some experimenting with small ramdisk images just to be sure before doing something with the real disks. And/or after taking dd_rescue clones of the real disks instead of even risking touching them at all.

Excuses like "I can't get one of those cards sooner than 4 days from now (by the way it's $800)" or "The card and drives are ok but I don't have another motherboard handy that has the required PCI-X slot for the raid card." or "The raid card firmware doesn't provide an option to do what I know needs to to happen to save 99% or 100% of the data and accept a tiny bit of corruption on a part of the disk that isn't even used by any files you wanted..." or "The boot message is ambiguous, and the cards manual doesn't even mention the topic, so we don't dare answer yes or no until we get the manufacturers tech support on the phone, and we can't reach them right now for some reason" or "raid6 would have saved the day but they didn't have raid6 when this card was made" etc...

All of those show stoppers are not show stoppers if the array were software raid. Since it's hardware agnostic, you are free to piece together whatever solution is physically possible with any/all of the materials at hand (ie, the local BestBuy out in the middle of nowhere, or even less than that, just the other pc's in someones office and your and their homes in the middle of the night in the middle of nowhere) It's very difficult to encounter a situation that can't bet met somehow when every scrap of computer tech within reach could potentially be used.

You have to know a little more but the important point is it's possible vs not-possible.

--
bkw
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