Virtual Machine Size

[Brandon7a]

We have LUNs that are 500 GB large and in RAID 5. What are the cons of creating LUNs 500 GB or more in a RAID 5? I'm thinking about creating an extent to add more space to it. We have a database virtual server that is about 250 GB on that LUN. We are using a CX300 Fibre Channel SAN with 2 HBA's in each ESX host.

[vmroyale]

Hello.

We have LUNs that are 500 GB large and in RAID 5. What are the cons of creating LUNs 500 GB or more in a RAID 5?

Sounds like one of them is running out of space and then having to add extents. I would personally avoid the extent and just create a larger LUN and then move this database VM (and possibly others) over to that LUN. That or split the disks up in the virtual machine across multiple LUNs.

Good Luck!

[msemon1 · Accepted solution]

It is ok to create LUN's that are more than 500GB with RAID5. Our SAN is a CX3 -80. We have some LUN's that are 1TB and 2TB. I agree with previous post in not creating extents. Just like in Windows with spanning volumes, if you lose an extent or volume you lose data. The larger LUN's may be prone to suffer some performance degredation and SCSI reservation issues because you have more VM's hosted on them. This is why VMware recommended a LUN size around 500-600GB. For the most part our 1-2TB LUN's have worked fine.

Mike

[Brandon7a]

What the cons of adding an extent? I didn't realize they were frowned upon.

[msemon1]

Data loss.

[khughes]

It's one of those things that "works" but no one really wants to use unless its a last resort. Like others said there is data loss that could happen, but also could get a little confusing to keep track of. It's cleaner and easier to manage to create a new LUN and move the data.

• Kyle

[bggb29]

Yes data loss would be my fear also. Although not high on a san. You lose on lun and you will lose all data in both luns.

We have been running a san for 6 years and only have never lost a lun.

We have never used extents so I have no idea how san snapshots work on2 luns. Something to test at least in my opinion.

Create a larger lun and migrate the servers if you have space