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We want to increase disk space of one of our server. Currently it has 8 physical disks(4 x 480 GB, 4 x 1.9 TB) and 3 virtual disks(RAID 1 (2 x 480GB), RAID 1 (2 x 480 GB), RAID 10(4 x 1.9TB)). We want to increase disk space on virtual disk 3 which is configured with RAID 10(4 x 1.9 TB).

We are planning to add 2 new 3TB disks into virtual disk 3 RAID array. In this case, we are not sure about how RAID is going to behave.

Since newly added disks have larger capacity(3TB) that the older ones(1.9 TB), we are not sure how much we effective space we are going to get out of it. Is it going to be 1.9 TB same as all older disks or is it going to be entire 3TB.

Can someone please help me with understand how will RAID behave in this case?


Server information :

  • Type : DELL PowerEdge™ R640 DX152
  • Operating system : Windows Server 2012 R2
  • RAID Controller : PERC H730P Mini (Embedded)
  • You currently provide insufficient information. How did you create the RAIDs ? Are they made by a hardware server controller or by software (like from windows disk management) ? Behavior can differ. – Overmind Oct 21 '19 at 8:10
  • Server is configured with hardware level RAID. – Ketan Oct 21 '19 at 8:22
  • Then all you have to do is access the hardware controller web UI and add these disks to your current RAIDs, respecting the requirements of doing so. – Overmind Oct 21 '19 at 8:23
  • I have updated the question with server information. – Ketan Oct 21 '19 at 8:26
  • @Overmind : We are adding larger disks than the existing disks. I want to know how much space will I get after adding larger disks? – Ketan Oct 21 '19 at 8:29
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From the PERC H730P Mini web interface you can add new disks to your existing RAID array.

Adding 2x 3TB drives to your existing RAID 10 made out of 4x1.9TB, assuming you manage it without any problems, will increase your space with those 3TB (around 2.7 real TB).

According to the official Dell documentation, page 25, increase of capacity by adding disks into a RAID 10 is supported.

But it all depends on controller being bug-free - in theory there is nothing what prevents you from extending with the controller and stripe across 3 mirrored pairs 3x2 disks from 2x2 original. Most of the time, such maneuvers work, but as in anything, there's a risk. I had a situation where simply adding a hot-spare changed the diskID causing the whole RAID to be unaccessible by the OS. Had to result to restoring from backups as time was too limited to try other solutions.

You should take all precautions to save all your data before attempting to expand your RAID 10 array.

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  • >> Adding 2x 3TB drives to your existing RAID 10 made out of 4x1.9TB, assuming you manage it without any problems, will increase your space with those 3TB (around 2.7 real TB). This is confusing for me. Because if you look at comments on above questions you can see @djdomi's comment which looks contradicting to yours. – Ketan Oct 21 '19 at 11:26
  • It does not contradict anything. Your objective is to add 2 disks not replace 2 disks. – Overmind Oct 21 '19 at 11:56
  • So you are saying that if we add 2 disks of 3TB each into RAID 10 array of 4x1.9TB then the effective size of RAID will become 6.8 TB (3.8 TB from old disks & additional 3 TB from newly added disks) ? – Ketan Oct 21 '19 at 13:34
  • hi ketan i aint k ow if the guys thinking about jbod but in a raid 10 there cant be a different size. if i have 4 identical drive and want to incraise the size i have either add or replace the device. if all has been replaced then i can expand the complete spanning tree. this due to that this is logicial thinking 2x raid1 which split both with a raid 0 – djdomi Oct 21 '19 at 19:14
  • @Ketan you can add about 2.72TB (in true space), yes. – Overmind Oct 23 '19 at 7:03

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