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I'm thinking of buying a HP Proliant microserver to replace an old dusty laptop which I now use as a home server and a Netgear ReadyNASDuo which is not raided at the moment.

I want the server to replace my NAS and home server, so here some questions:

From what I understand I can't hot-swap, right?

I was thinking of having five drives in total but slowly upgrading it. So I was going to start with two drives (one drive to drive the OS, and the other to have as future RAID). But since I want to plan ahead I would like to have RAID 5 (which means more storage than raid 1, when 4 drives are inserted, while everything is still backed up, right?).

Do I have to have 3 drives from the start to have a RAID 5?, or can I use/change to RAID 5 when three drives are added without actually formatting a drive?

I've looked if this is doable but did not find any info on it.

Can I even format one drive as a RAID and then add other drives?, or must I start with 4 drives from the start?

And any other tips on doing software raid on ubuntu would be greatly appreciated.

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up vote 1 down vote accepted

According to the specification of HP Proliant microserver, it doesn't support hot swap.

You have to have at least 3 drives from the start for RAID 5.

You can increase the number of disk of RAID 5 by adding new drive without destroying existing data.

using mdadm as software raid is great. You can have more information from here.

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If I have a RAID 5 and three drives and want to add a fourth, I cannot do this by using mdadm?, and have the fourth drive be part of the raid5? – Joakim Engstrom Jan 7 '13 at 15:43
You could, but all data in the RAID will be destroyed if you change the RAID size. If you add the drive as a spare disk, no data would be destroyed. The spare disk would replace any failed disk have happend. – neo Jan 7 '13 at 15:58
I've looked around and does not this article do that – Joakim Engstrom Jan 7 '13 at 20:55
Yes. It is possible to use mdadm to grow raid. – neo Jan 8 '13 at 2:00

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