Re: [SLE] SuSE 9.3 x64 and SATA II raid

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• In reply to: Michael A. Coan: "Re: [SLE] SuSE 9.3 x64 and SATA II raid"
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Date: Tue, 12 Jul 2005 00:03:20 -0400
To: suse-linux-e@suse.com

On 7/11/05, Michael A. Coan <mikecoan@woodlawnfoundation.org> wrote:
> >> My plan is to use RAID 0 (I know that means no redundancy) and then
> >> use an additional hard drive for backing up the data files.
> >
> > RAID 0 is striping and will give you extra speed. But RAID 0 has the huge
> > drawback if one drive fails, the whole thing comes crashing down, and
> > you'll
> > have to reinstall everything.
>
> I realize that. I guess my initial thought was tht it is very easy to
> reinstall SuSE 9.3 (less than an hour). Since Windows server will be a
> guest OS, it will only be 6 or 7 files, so I copy over the files in 10
> minutes and it is reinstalled. I figured that the time saved by using RAID
> 0 over say three years, would more than offset the time it takes to
> reinstall. Maybe that is foolish.
>

I would avoid RAID 0 if you can. Unlike the other RAID levels, with
RAID 0 the more drives you have in the array, the more unreliable it
is!!!

ie. if your drives have an average life of 3 years then:
Single drive: 50% chance of failure in 3 years ( 1 - .5 )
Two drive RAID 0: 75% chance of failure in 3 years ( 1 - (.5 * .5))
Three drive RAID 0: 87.5% chance of failure in 3 years ( 1 - (.5 * .5 * .5))
etc.

> Maybe i should use a 3ware controller and do raid 5. this time I will
> know what the beeping is :) Or would you recommend RAID 10 instead.

RAID 10 is the fastest and most reliable, but also the most expensive.

Especially on writes RAID 5 can be very slow, but the more drives in
your RAID 5, the faster it should be.

> >
> >> i am not inclined to use raid 5. Our current server had raid 5 with a
> >> Perc controller and 3 Ultra 160 SCSI drives. When one of the drives
> >> failed the controller began beeping like crazy, but everything worked
> >> Too bad i didn't know what the beeping meant. By the time I figured out
> >> what the beeping meant, a second drive failed and I had to reinstall
> >> Windows Small Business Server on the remaining drive.

I think Linux MD now supports RAID 6, or maybe that is some specific
hardware controllers. Not sure. RAID 6 is like RAID 5, but it has 2
parity drives. In the above you still would have been okay until you
lost the 3rd drive.

Personally, I would not consider RAID 6 unless I was planning on
having 6 or 8 or even more drives in the RAID set. With less than
that you might as well use RAID 10.

Greg

-- 
Greg Freemyer
The Norcross Group
Forensics for the 21st Century
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• Previous message: Joseph Loo: "Re: [SLE] Equipment"
• In reply to: Michael A. Coan: "Re: [SLE] SuSE 9.3 x64 and SATA II raid"
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]