Mirroring and the no. of disks in the mirrored group

[Anu Mathew]

Hi all,

We have to establish a mirrored logical volume over 6 nos of 73GB disks. We will be using these logical volumes for write intrinsic operations and will be mounting two file systems over this. The question is whether to create two separate mirrrored Volume Groups, if it involves some performance impacts.

We are employing FC60 disk array and so we have the option for going for a hardware RAID 1. In FC60, if RAID 1 is implemented, RAID 0 also comes along. We are opting for optimum performance. In FC60, should I create separate mirrored LUNs, create the VGs and then LVs or one entire mirrored LUN with single VG is enough? Which way I can have the max performance?

Thanks a lot in advance for your patience, time and expertise.

Regards

Anu

[Thierry Poels_1]

hi,
sorry no statement from me on that performance :(
but just want to note : you have two options hardware mirroring on the disk array or software mirroring through Mirror/UX.
The hardware option is fixed, and might give a little bit less overhead.
But through Mirror/UX you have a lot more flexibility:
- you can split up the mirror for backup purposes, and sync again afterwards.
- you could temporarily stop mirroring if you are desperate for some diskspace
- you can easily move a mirror to other disks

regards,
Thierry.

[Pedro Sousa]

That's all true Thierry, but I would use the HW mirror on the same LUN instead of Mirror/UX.
The mirror/ux is flexible, but it's very easy to make mistakes with the configuration like creating a lvol where it shouldn't be...

[Pedro Sousa]

Another thing I forgot, the Raid 1/0 will give you the best performance beacuse the FC60 will control all the I/O traffic and will split it automatically. I know you can use the stripping facility with LVM too, but it's not so good.

[Stephen Bouzan]

Another note on performance, check the hardware specs on the FC60 & the hw RAID. Sometimes performance can be maximized with a certain number of LUNS. I sure if you do some research you will find what the HP engineers recommend.

I would use Hardware RAID on this disk sub-system.