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Old 10-18-2005, 03:09 AM   #1
Registered: Jul 2004
Location: Nottingham, England
Distribution: Fedora 17, Centos 6.3 x86_64
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Adding additional drives/resizing drives in RAID arrays


I've currently got a setup with 4 hdds, of different sizes, raided to provide speed and resiliancy.

I want to upgrade the disks as they are getting full, but I've a significant problem in that I can't backup the drives, and I can't reallisticly add any more quantity of drives.

What I have at present is 2x160gb and 2x80gb. They are arranged as a 4x80 raid 5, and the remainder of the 2x160 are a raid-1.

What I want to achive is replace some or all of the drives with larger ones, without losing any data.

Is it possible with a raid-5 to add additional drives to the array once it's been set up, apart from "spare" devices?

Does anyone have any suggestions as to a suitable migration plan?

Thanks in advance.

Old 10-19-2005, 01:21 PM   #2
Registered: Feb 2003
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Mdadm will solve all your problems.The explanations to your questions would be a lot of writeing and you are best to read the mdadm man pages.

Heres a review with some detailed info on some of its features and options.
There are appropriate links to mdadm page in the review.

I have added extra drives to my raid 5 array.It origionally consisted of 4 35 g raptors and I added 3 more.3 was active one was spare...with the 3 new ones I formatted exactly how I had the others formatted(4 partitions) and then added makeing 2 active for a total of 5 and 1 a spare for a total of 2 spares.It wasnt hard.In my case the extra drives was adding free space.The rebuild utilised the free space without disrupting filesystem.

The easiest way is if you have LVM over your raid setup.This allows for an easy transition of growing a filesystem size.

Heres a good howto on manageing raid and lvm

Also part of the raidtools package,"raidhot[add|remove]" is used to add or remove a disk from a RAID array.

Following are examples of their use:


raidhotremove /dev/sda1 /dev/md0 (hot remove the partition /dev/sda1 from /dev/md0)

raidhotadd /dev/sda1 /dev/md0 (hot add the partition /dev/sda1 to /dev/md0)

Have a look here,it should give a link to what you need.

The above is the last page to software raid how to and is an excellent guide.

Hope this helps.


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