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Re: raid setup recommendation

Chris Parker wrote:

i have just aquired a new Dell Poweredge 6850 with md1000 raid.  It has
the perc 5/i and perc 5/e.  The 5/i has 1 75 gig 15k drive and the 5/e
has 14 146 gig 15k drives.  They are all SAS.

It is going to be used as a vmware server for win2k3 guests.  What would
be the optimal raid setup?

Chris Parker

Does the 5/e controller not dictate the RAID setup?

If you are using hardware-based RAID, then I like 10. The 5/e contoller doesn't support my other favorite, RAID 6. It supports 50, which I don't know anything about.

Also, no official Debian support, of course.

I was with you 'til then.

Well, I was with you 'til you said "vmware". I have been reading up on RAID, and nearly all types of RAID have their proponents. I favor 10 (1+0) for even numbers of disks, or (possibly) RAID6, under software RAID. But I don't know enough about vmware's quirks to say if there is anything to consider specially for it.

RAID 10 can tolerate losing a fairly high number of disks at once (as long as two paired disks don't both fail), has acceptable performance, and has pretty quick rebuilds. (RAID6 is apparently (somewhat) supported by Debian, can tolerate losing any two disks at once, and has a higher usable capacity than RAID 1 or 10. But not easy to do with your controller.)

vmware can use virtual disks, so nothing special need be done to use the array. But whether any of the choices are "optimal"...

Does vmware have anything to say on the subject? Wouldn't hurt to check the documentation.

If you set up more than one volume set, you could distribute VMs across the disk array. Losing one set wouldn't mean losing them all, and the VMs running on the intact sets don't even need to know that anything has happened.

If you could set it up this way, you could do three sets of four disks, with two hot spares, or one hot spare, and one cold spare.

Mark Allums

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