Large LV, expereinces and recommendations?

[Tymish]

I'm about to put a pair of 16TB units online. Each has three 3ware H/W RAIDs.
2x4.5 TB and 1x6.2TB
Created a VG using one 4.5 and 1 6.2 Keeping the last 4.5TB as expansion space.

I'll be using these as a NAS pair right now.

Half the users will be mapped to unit 1 with data replication to unit2 and the other half mapped to unit2 with data replicated on unit1.

So I get some load balancing and hot backup as well. Should one unit have a disastrous failure I just map those users over to unit2 & allow access.

Now my question.

Is there any reason I shouldn't create a single 10+ TB LV?

[To-M]

Unless you need a separate RAID set for a specific reason and separate cache for the RAID sets to keep spindle count low then no. Many engineers will not put more then 22-24 drives in a RAID 5 or 6 but with RAID 10 they will and some wont place more then 12-16 drives on a RAID 5 or 6.

[Tymish]

In my case I have three RAID 5 units with hot spares in each system. Two 11 drive and one 15 drive RAID I'm combining two of them into an 11TB VG. Then I want to create a single 10TB LV for my storage volume.

[Tymish]

So having a 10TB LV shouldn't be an issue then? What about FSCK? That could take a looong time. How does DSS handle that?

[To-M]

10TB is fine - we format the disks to xsf when you create the volume group. If iSCSI LV is created then the OS's will do the rest.

[silicon]

This may be out of date now, but from a previous nightmare we had with DSS, make sure you are running in 64bit mode and have lots of Ram, otherwise fsck etc. can never complete a scan on a large volume! Cheers.

[symm]

Hi Tymish

The more ram that you have the faster FSCK will run,
Just remember to run a memory test before fsck.
FSCK will move data from disk to ram to fix it
if you have bad ram it will corrupt your data


as for volume size, you can always expand the LV size but you cannot shrink a LV.
MAy be better to start with smaller LV and then expand them as you need to.