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Migrate from RAID 0 to RAID 5 without data loss

DaveVision
Occasional Visitor

Migrate from RAID 0 to RAID 5 without data loss

Hi All,

We use a ML370 G3. Currently this machine is a SBS 2003 server and running on RAID 0. The data located on this machine (including applications) are critical and should remain in tact when one disk fails. Is there a way we can migrate from RAID 0 to RAID 5 without loosing data and still having a fully operational system?

What we have now:
- We have 4 disks active and 1 doing nothing.
- 1 volume with 2 partitions on RAID 0

Also we have a minimal space left on the system drive. This needs to be increased ASAP. How should I approach this? Using something like Acronis Disk Director Server to enlarge the C drive? (After successful migrating to RAID 5)

Any help is appreciated

Dave
3 REPLIES
kris rombauts
Honored Contributor

Re: Migrate from RAID 0 to RAID 5 without data loss

Hi Dave,

yes this is possible without loosing data IF you already have those disks connected to a SmartArray controller in RAID0. If however the RAID0 you are talking about is a software RAID0 managed by the Operating system then their is no way to migrate online from RAID0 to RAID5, backup/reinstall/restore data scenario is the best answer then.


If you migrate from RAID0 to RAID5 on a SmartArray, keep in mind that you need additional disk(s) in order to be able to do this, with the one spare disk (assuming it has the same capacity) you will end up with a RAID5 with 5 disks but only still have the same total capacity because of the overhead of RAID5. If you need more total capacity then you need to migrate to a raid5 with 6 disks (max for a ML370 G3).


The system disk free space issue is another subject that you might be able to address with non Microsoft utilities because diskpart.exe itself that comes with w2k3 has some limitations see :http://support.microsoft.com/kb/886986/en-us

http://support.microsoft.com/kb/300415/en-us

and read the section about "extend", it can only extend into contigious space that folows the partition you want to extend, this is not the case when you extend the array on a SmartArray since you have 2 partitions you mentioned above.

One way to fix this is to:
- backup data partition
- delete that partition
- extend it
- create new (second) partition again
- restore data


I cannot comment for the other tools out their on the market.


HTH

Kris


DaveVision
Occasional Visitor

Re: Migrate from RAID 0 to RAID 5 without data loss

Hi Kris,

Thanks for the response. Sorry for the delay regarding my reply.

I've two questions:
It's a basic ML370 G3, no external storage, just the disks which fit by default into the machine it self. (max. 6) Do you mean an external smart Array?

Do you mean that when you need to increase the total capacity, while using RAID 5, you'll always need to add two disks?

So the procedure will be:
1. First migrate to RAID 5 with the current 4 disks.
2. When at RAID 5 level, add the last spare disk (two actually) then automatically the volume will increase? (it's hardware RAID)
3. Resize the root partition to use the extra added space on the volume (which has been added since the two disks are added)

Please note that the issue here is the system partition, which has almost reached the maximum space. We'll need to resize this, and not delete â ¦

Did you ever face this problem, or maybe someone else that the root partition (system disk) had less space left?

Many thanks for your perfect explanation!

Dave.
kris rombauts
Honored Contributor

Re: Migrate from RAID 0 to RAID 5 without data loss

Dave,

answer to your questions:

1) Do you mean that when you need to increase the total capacity, while using RAID 5, you'll always need to add two disks?

No, one disk is fine BUT this case is special since you need to first migrate from the current RAID0 level to RAID5 which will cost you the capacity of one disk to go from a non redundant array to a redundant array but it does not give you extra storage capacity yet.

Example:

RAID0: 4 disks * 73 Gbyte = 292 Gbyte net available
RAID5: (4+1) * 73 GByte = 365 Gbyte - 73 Gbyte overhead for RAID5 redundancy = 292 GByte left, so the same as with RAID0.

So in order for you to add capacity you indeed need a second disk this time to extend the 292 to 365 GByte net capacity.


2) the procedure

no, you need already one disk to migrate from RAID0 to RAID5 and then the second one to get more space. The when the SmartArray migration is finsihed in the ACU (utility to manage the SmartArray) you can check the logical in the raid5 and then work at the OS level.


I advise to also inspect your c:\ disk manually for any temporary files etc that can be cleaned up i.e.
Maybe you can deinstall some programs and reinstall into your D:\ drive i.e. as a quick workaround.


Kris