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lanrat
Asked: 2009-07-21 10:17:11 +0800 CST

Linux RAID 5 with non identical disks

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I want to use a software raid on a Linux server I am creating. I have 2 identical Maxtor 250 GB hard drives and one Western Digital 250GB hard drive. I know I know I can easily set up raid 1 with the 2 Maxtor drives, But is there a way I could use the third Western Digital hard drive to make a Raid 5 array?

If so are the procedures for doing this any different than using 3 identical drives?

I am planing on using Ubuntu server for this (Same drives for data and OS) are there any nice guides for doing this. (I have never setup RAID before)

Thanks.

EDIT: I have no idea how to set up the raid during the Ubuntu server install, so I also need instructions on how to do this. (A link to a guide will do just fine)

linux raid raid5 software-raid

6 Answers

  1. Best Answer

    There shouldn't really be any isues mixing disk vendors, Linux software raid is discussed pretty thoroughly here, you shouldn't have to do anything differently just because the drives are from different vendors.

    "There are no other special requirements to the devices from which you build your RAID devices - this gives you a lot of freedom in designing your RAID solution. For example, you can build a RAID from a mix of IDE and SCSI devices, and you can even build a RAID from other RAID devices"

    (From the Linux raid wiki)

    As far as setting up the raid during the installer goes, you have to use the "alternate" (textmode) installer, full instructions for this are here on the Ubuntu wiki.

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  2. Will work just fine.

    Unlike osij2is I always recommend software raid. I've run many many large disk installations, and HW raid have always given me more headache in the form of drivers, performance, stability, userspace utils for raid maintenance and recovery when moving the disks between controllers, slots or controller manufacturers.

    Actually, nowadays I recommend ZFS.

    • 3

  3. Seems to be a lot of RAID questions today. Hmmm. First, I'd advise against software RAID no matter what OS. Buy a RAID controller (a repetitive mantra of mine). If this is just a test system to play with, fine, I understand you can do without, but if you really want this RAID array to work (and work well), I highly recommend getting a RAID controller. Lots of Linux support these days for RAID controllers so I wouldn't fret about driver support much.

    Second, the brand of the drives doesn't matter so much as the size does. Having 3x 250GB drives will allow you to have RAID 5 array, granted it's nicer to have all the same drives for aesthetic reasons and possibly technical reasons. I assume all 250GB drives run at 7200rpm and have 16MB cache? It's better if at the least they're all nearly the same size, speed and buffer size as it helps to have equal specs amongst the drives as well.

    Lastly, here's a good intro guide to Linux RAID arrays. There are lots of good guides out there, but tldp.org is a good place to start. I'm sure there's more info addressing RAID for Ubuntu, but I'd say if this is your first time with RAID, it's best to get the general information first and then deatails (step-by-step) on your distro.

    • 2

  4. Just because you can doesn't mean you should. Never ever use RAID-5 (or 4 or 3.) http://www.baarf.com/

    I'd suggest setting up a RAID-1 with a hot spare. Use one of the maxtors for the hot spare (not the WD.) You want to make sure the RAID will work with mismatched drives. You don't want to find out AFTER a drive failure that your hot spare won't work.

    • 1

  5. Absolutely no problem. You probably won't be able to get the full capacity of the drives due to different geometry, but you'll be just fine with those three drives.

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  6. Your array will be of the size of the smallest disk in the array, and at the performance of the slowest disk in the array. This rule counts for any raid, software or hardware.

    And yes - it will work just fine :)

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