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I have installed Ubuntu on a DELL 2850 and I have configured an array of 5 disks (SCSI 73GB 10K) in RAID5.

I wanted to simulate a drive error so in the middle of something I just took one of the drives out and put it back again after a bit. Then the drive shows an orange light and seems to be rebuilding but actually is taking hours and hours with no results. So I went to the PERC utility (Ctrl+M) and the disk shows "REBLD". But it never gets to an online state. So I went to Objects - Physical drives - Rebuilding - View rebuild process. And in here I can see a bar moving from 0%... but if I reboot before finishing and get into the PERC Utility again, it seems to start again rebuilding from 0% - so it is not rebuilding automatically.

My concern is: what would happen in a real situation? Do I have to just switch the server off and go to the Perc utility to start the rebuilding manually? I thought the whole point was to have this done automatically and without the need of stopping the server. Or does it perhaps rebuild automatically indeed but needs to have enough time without rebooting because otherwise the rebuilding process will start from scratch? It seems to take more than 3h for a 73gb disk!

My second question is: can I mix then hard drives? So if I have a RAID of 5x73GB 10K can I use different size (146GB) or speeds (15K)? Apparently someone said it is OK in here Poweredge 2850: replace disk with larger in RAID?

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You should probably ask one question per question. As for replacing with a larger disk that will work but you will only get the capacity of the smallest disk in your RAID. – Atari911 Jul 3 '13 at 3:58
up vote 0 down vote accepted

In some of the older PERC4 firmware, rebuild could not start automatically, you had to go into OMSA or the controller BIOS and mark a free drive as hotspare - then it would start a rebuild.

Rebuild can be throttled via settings in OMSA, try to change the resource percentage and see if that speeds things up. Also, make sure you are at the latest firmware on both the controller and the drives.

About interoperability - any mix should work, just keep in mind that the spare space will be unusable, and the array will operate at the speed of the slowest drive

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Eventually it rebuilt. But it seems that it has "no memory" so if I switch the computer off, it has to start again – Kiara Jul 5 '13 at 2:39

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