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Removing a drive from a RAID 5 Array

S_Vincent asked
Medium Priority
Last Modified: 2008-02-01
Hi, i have a setup on a HP DL380 using a 6400 raid card where i currently have 4 disks in a raid 5 array, 3x144Gb + 1x72Gb giving me 216Gb(3x72), i have already replaced 3x72GBs with the 144s and now i wish to remove the last 72Gb out of the array and then expand all the three 144s to full capacity giving me 288(2x144).  OK, can you pls tell me if this is possible (and how to) using HPs Array Config util as windows 2003 obviously only sees 1 drive at 216Gb cause its not handling the array.

I hope this make sense.....

Thanks - Shane
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Until you have replaced the 4th drive in the array the ACU will not show you the extra space. After it is replaced you will see parallel scsi array A with logical drive 1 on it plus some free space. Use the wizard to expand or extend the array or create another logical drive on it.


Hi David, Thanks for your response but i am not replacing the 4th drive (72Gb) i am wanting to be remove it completly.
Cannot be done without backup/restore or imaging software. The conversion algorithms aren't clever enough for that.

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Artysystem administrator
Top Expert 2007

David_Fong right, you cannot just pull out your disk without backing up, reconstructing raid abd restoring back
Also you will have a performance degradation (for raid-5) after disk is pulled out.


Ok, now i have a problem, i have no drive bays free and i still wish to remove the 72Gb drive.  Will downgrading to Raid 0 help at all? Is there any other way other than backup/resore or imaging as this would have to be done with an external drive (very slow and long downtime).

Thanks - Shane
Artysystem administrator
Top Expert 2007

I don't recommend you to downgrade to RAID-0 since, as I see, you have no backup media. DAID-0 have no redundancy.

It's time for you or your company to buy additional hardware (additional 72Gb HDD for you will cost much cheaper then any solution that I can suggest).

"Is there any other way other than backup/resore" - NO.
Pulling disk is _possible_ but NOT RECOMMENDED. Your RAID will be degraded not only because status changes to 'degraded', but it will become  phisycally slower and this is not a solution. Moreover after pulling 1 disk you will loose redundency completely and any disk failure in such degraded RAID-5 will lead to loosing all data on it.


Thanks Nopius,
All important data is backed up (using robocopy) over WAN, so i guess the question regarding RAID-0 is can you change a 4 disk RAID-0 array to a 3 disk array therefore not using one of the four disks..  then remove the 72Gb and then change the array back to a RAID-5 using the 3x144Gb

The main reason behind all this is we have simular setups in 5 other locations and the cost of 5 new 144Gb HDD is about $3,000AUD...  whereas to remove 1x72Gb at each location is free....
Artysystem administrator
Top Expert 2007
After backing up _all_ data, you have to _destruct_ previous RAID device, pull out your disk and perform new RAID reconstruction.
Then, as you can guess, full bare metal restore is requiered.
So if you want  to get 3x144Gb RAID-5 (which is 2x144Gb raw capacity) and you have 4x144Gb disks in RAID-0 group, your actions are:
- make _full_ backup of your data on RAID-0 (and then full restore, for training)
- destruct RAID-0 completely
- pull out 1 HDD
- construct RAID-5
- restore all data.

It takes time and some backup/restore experience, be aware.
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