HP Left Hand 3 Node Cluster Space Requirments To Convert Volumes From RAID5 to RAID10

[NavSup]

HI,

I am looking for some advice on working out the space requirments needed to convert RAID5 volumes to RAID10 on our 3 node cluster. 

We have 3 nodes with with 25 x 900GB drives (1 hot spare)., total cluster size 56TB, used space 39TB, free space 16TB. The RAID on the nodes is RAID5

How do i work out the space required to convert an existing 50GB volume that is RAID5 thin provisioned with consumed space of 136GB (+37GB shared space) to RAID10 ?

If i create a volume thats 10TB at RAID 10(2 way mirror) then the volume created uses 20TB If i create a 10TB volume using RAID5 how much space does this use, Is there a simple equation to follow.

Thanks

[oikjn]

are you talking about the storevirtual system and the hardware raid configuration on each node or are you talking about the network raid leve?

On the hardware level, it would be better to remove the node from the management group if possible before making the change, but I"m guessing you might not have that space, but if your data really is THAT important, you should figure out how to achieve it.

If you are talking about network raid.  Then its more simple.  the required space... aka the consumed space is 2x the size of the data on the LUN (assuming thin provisioniong... which is should be).  The worst case would be to use 2x the reported LUN size and that is as large as it can get (excluding snapshots).

[Stor_Mort]

If i create a volume thats 10TB at RAID 10(2 way mirror) then the volume created uses 20TB If i create a 10TB volume using RAID5 how much space does this use, Is there a simple equation to follow.

Unfortunately, nothing very exact. The amount of NR5 parity overhead depends on the number of storage nodes in the cluster. There is also some variation because of optimization techniques used to increase performance at the expense of space utilization. The parity overhead will vary with the characteristics of write operations to the volume over time.

[oikjn]

if you are thinking of using network raid 5 for anything other than archive static data... don't.  It's write performance is terrible and even the documents say it is only for static data.

[BenLoveday]

We've done many online NRAID migrations, 5 -> 10, 10 -> 5, etc and have all gone fine without any problems. As for capacity calculations I'm not sure, as others have said NRAID10 is fairly straight forward but NRAID5 is not as simple.

From memory the migration process determines whether the cluster has sufficient free space before starting the migration so give that a go.

I think if the migration is not possible the Data Protection Level won't be shown in the dropdown list under the Advanced tab when editing the volume.

Cheers,

Ben Loveday