2008-11-30 10:08 PM
Inside a 400 GB flex volume. i have created 2nos 75 GB LUN and mapped with all VMWARE ESX server. In the "volume manage" page i can see 99% as a usage area.
Then I turned off the space reservation of those 2 LUNs .Now the volume usage is showing as 39 % only (Which means 378 GB is available space on 400 GB volume)
.Is it right to turn off the space reserveation for vmware LUNs?
2008-12-01 01:24 AM
When you are not using snapshots based on Netapp technologie you can disable LUN space reservation. But as you use SnapManager VI you should turn on LUN space reservation.
Don´t forget to disable snapshot schedule to the containig volume.
2008-12-01 03:40 AM
I am not sure if this is the case.
When you set LUN reservation to on at a new 20 GB LUN it will claim that 20 GB immediately. If you do not set the LUN reservation, it only claims as much data from the Volume in which the LUN resides as data is written to it.
Let's say you have a Volume of 100GB and a 20 GB LUN. In the 20 GB LUN with no space reservation, 5 GB of data is written. The volume will show 95 GB of free space
When setting space reservation to on, the volume will show 80 GB of free space eq it will claim 20 gb immediately even when there is no data on it..
When you do not set the LUN reservation, it is called Thin provisioning. Netapp wrote an excellent Technical Report on this. You can find it here:
As you can read in the document, space reservervation for snapshot restore is called "fractional reserve"
I think this is a must read for everyone who is using Netapp!
2008-12-01 05:04 AM
I must say, all these terms are confusing on how they work and when to use.
i Think most engineers agree with me on these terms like snap reserve, lun reservation, fractional reserve, space reclamation and thin provisioning.
looks like a whole new language