Install larger Hard Drives in Raid 5 Array

Posted on 2014-01-15
Last Modified: 2016-12-08
Dell PowerEdge 2950 with Raid 5 Array using 3 SAS 146 Gig Hard Drives.

Simply put, we've run out of hard drive space.  I have 3 more open slots in which I could insert more hard drives.  However, if I'm going to increase storage capacity, I don't want to just add 3 more 146 gig hard drives in those open slots.

I'd just as soon replace the existing 146 gig hard drives with 3 larger hard drives.

Would these larger hard drives be "hot swappable"?
Would the Raid 5 array need to be broken in order to make this work?
Can I just pull out a 146 gig hard drive and insert a 500 gig hard drive?

Please advise.
Question by:baleman2
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Expert Comment

ID: 39783353
In a RAID 5 all the drives need to be the same size.  If you replace one with larger, assuming the raid controller uses it all, it will be treated as a 146 since thats what the rest of the drives are.

Best solution for you is to get three 500 or bigger drives and create an additional RAID 5.
Then migrate your files over and remove the original ones.  Then you can consider adding more 500GBs to the new array assuming your controller allows adding.
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Assisted Solution

rindi earned 250 total points
ID: 39783384
It depends on the RAID controller's features. Some, once you have changed all the disks and waited for the synchronization to complete, have a function that allows you to expand the array to include the available space of your new disks.

Personally though, whether the controller has the above functions or not, since you have 3 empty bays, I'd just add 3 new larger disks and create a new array for those.
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Expert Comment

ID: 39783408
Stick in 3 of the 500GB disks and build the RAID5 array and initialize it via the controller. Boot to LINUX with a USB stick and then download the freebie partition magic software. This will let you safely copy the data & resize the partitions & file system. (If it fails for whatever reason, your original data is there and it remains untouched).

Then shut system down, change boot path to the other lUN, and test to make sure it boots OK.  If so, then you are good to go.  You could even then add more 500GB disks and resize the existing RAID5 via the controller's utility.

(Booting to LINUX insures the data will not change on the source side so it will be a clean image copy backup & resize all at once);
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Author Comment

ID: 39783420
Once 3 new larger hard drives are inserted into the empty slots, a new Raid 5 array would need to be created for just these 3 hard drives?

What I hoped to avoid was the re-installation of an OS, installation of software, transference of that software's data to the new array, etc.

How best to get EVERYTHING from the old array to the new array?  Would cloning software do this?
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Expert Comment

ID: 39783438
1. Build and initialize a new array, LUN#1, the other is LUN#0 (all from BIOS)
2. Change boot path so USB (or DVD) boots first, then LUN#1 boots 2nd, LUN#0 not bootable at all.
3. Get your favorite LINUX distribution Live USB or LIVE DVD (google how to do this)
4. Boot to LINUX, it will mount LUN0 SAFELY in read-only mode.
5. Go to the app manager or package manager and find partition magic, or partitioning, or cloning software & download it.  This will go into RAM, not the HDD
6. Run it, and do a partition level copy of LUN0 -> LUN1, then tell it to make LUN1 bootable, and resize the NTFS at the same time.
7. Click the shutdown Icon, remove the stick, and watch it boot, it will be as before, only on the 3-disk raid set.

This will be the new "C" drive, everything will be as it was, with more free space. -- I am assuming you are running a flavor of windows, of course)

Lots of freebie linux cloning and partitioning copy software out there.  all downloadable via the native package manager (think of it as an app store with free apps)
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Expert Comment

ID: 39783482
You don't have to install any software, or reinstall an OS, if you add those 3 larger disks to the 3 empty slots. All you need to do is create the additional new array, and then within your OS (which is still present on your old array), you can partition and format that new array, and use it.

Author Comment

ID: 39783530
I'll add something more to the mix.  We're running Windows Server 2008 Standard as the OS on the Dell box.

Hyper-V is installed on the server and I have 6 Virtual Machines running on this box.  This is the reason I was hoping for a hot-swappable solution.

To dlethe:  does this additional configuration info change any of your instructions?
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Expert Comment

ID: 39783838
Neither The OS nor Hyper-V makes any difference. Just add those new disks, create a new array with them, and use diskmanagement to configure the new "disk" for your OS.
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Accepted Solution

PowerEdgeTech earned 250 total points
ID: 39784074
If you replace the smaller disks with larger disks, your array will still be the same size, and the only thing you will be able to do with the newly available disk space on each larger drive is create a second RAID 5 across the disks using that space.  This second VD/array will show up in the OS as a separate "disk", so you are in the same boat as if you just added disks as their own array in the first place, which is what everyone else is recommending.

(Also, 146GB is a standard SAS HDD size, while 500GB is a standard SATA HDD size ... you CANNOT mix SAS and SATA in the same array, so you would have to replace your existing SAS disks with larger SAS disks or do a backup/restore to a SATA array anyway.)

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