Mailinglist Archive: opensuse (3441 mails)

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Re: [opensuse] happy "dmraid" at boot
  • From: "David C. Rankin" <drankinatty@xxxxxxxxxxxxxxxxxx>
  • Date: Wed, 21 Jan 2009 02:55:23 -0600
  • Message-id: <4976E2FB.1040200@xxxxxxxxxxxxxxxxxx>
Greg Freemyer wrote:

Just a reminder that the basic Linux approach to software raid is to
use mdraid (software raid) if you can. If that cannot satisfy your
needs, then move to dmraid (fake raid).

Personally, I am seriously considering using mdraid in a project soon,
but I don't envision myself ever using dmraid. I guess you never know
so I won't rule it out.



I think you are missing out. I have heard people tell me how bad fake
raid is,
blah, blah, blah but I was never able to get an answer to the simple question
of why?. The first raid I ever put together was fake raid on a Gigabyte
GA-7N400S that has the nVidia nForce2 MCP RAID chip. That was in 2007. Since
then I have put at least 3 more, maybe 4, together and I have had zero
problems. I also have 2 systems running mdraid. Same results.

I have tried to find a performance difference to distinguish the two in
mind -- without any luck. From the hdparm and real world copy standpoint, I
don't see a performance hit compared to a single drive, much less between the
raid packages.

The dmraid bonus for rebuilding is that the hardware takes care of the
before you are even running on the array. Now, I don't know how it compares in
hot-swap features and ability, but for my 2 disk raid1 arrays, I've never seen
it stumble and I've had zero issues -- knock on wood...

David C. Rankin, J.D.,P.E.
Rankin Law Firm, PLLC
510 Ochiltree Street
Nacogdoches, Texas 75961
Telephone: (936) 715-9333
Facsimile: (936) 715-9339
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