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I have 4 disks on an Ubuntu Server box, can I create on partition that spans across those 4 disks?

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3 Answers 3

up vote 2 down vote accepted

Assuming the 4 disks are the same make and model, or at least similar, you want to set up a raid. You can do this in the server installer. Create a partition on each disk designated as a raid component, then create a raid array out of the components. You can then install the whole system onto the raid array, but it is a better idea to use the raid array as an LVM physical volume, and use LVM to divvy up the array into different logical volumes, and leave some space for later use. If you care about handling the possibility of one of the 4 disks failing, then you should use either raid5, or raid10. Raid5 will give more usable space, and better sequential write throughput. Raid10 will give better random IO throughput and may even handle a second disk failing, depending on which one it is.

See wiki.ubuntu.com/Lvm for more information on lvm.

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It depends on the use case I guess: if it is a file server I would go for lvm: adding a disc is so easy with lvm. You toss in another 1Tb disc and of you go. RAID on the other hand... it needs 4 of the same discs (and models). So expanding your 4x500Mb to 4x1Tbs will be expensive. a +1 cuz I should have included raid in my answer ;) –  Rinzwind Mar 11 '13 at 8:10
    
@Rinzwind, with 4 disks, the probability of failure is 4x as high, so using LVM by itself, which offers no redundancy, is not usually a good idea simply in terms of having a reliable server. It is quite flexible though, so using it in conjunction with raid is nice. –  psusi Mar 11 '13 at 15:07

You can when you set your system up using LVM. 1 of the bullet points on that pages is...

  • Creating single logical volumes of multiple physical volumes or entire hard disks (somewhat similar to RAID 0, but more similar to JBOD), allowing for dynamic volume resizing.

Helpful links:


Here is some more info on RAID and LVM: http://stackoverflow.com/questions/237434/raid-verses-lvm

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It seems that there's a "virtual filesystem" solution here:

http://romanrm.ru/en/mhddfs

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This was an OK option in the end, but LVM was so easy to set up, and generally a more complete and rich solution. –  David Parks Mar 24 '13 at 2:06

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