I’m a bit confused with the space some volumes are reporting.
- 710Gb Volume (Fractional Reserve 20% / Snap Reserve 0)
- The volume contains a 460Gb lun of which 452GB is being used.
- My snapshots report 117 Gb used
Therefore I would expect space used by the volume to be
Volume – Lun used size – FractionalReserve - SnapShot Used
710 – 452 – 142 – 117 = -1
The volume actually reports 669Gb used and 41Gb free?
So from the figures above resulting in -1, I'm assuming that I'm using some of my Fractional Reserve for snapshots, however each snapshot is only about 15gb so I would expect the volume available space to get to 0 before Fractional Reserve starts being used. I can't see how you can see how much of the Fractiona Reserve is actually being use.
I’m sure I’m doing something wrong but just can’t see it.
Solved! See The Solution
2011-09-14 04:23 AM
The Fractional reserve is a setting for how important it is for the snapshot of this LUN to be able to be created. Set it to 20% and it will "reserve" 20% of the size of the LUN to "guarantee" the creation of a snapshot that needs 92G of space. If you create a snapshot that nedds more space then 92G, it will fail...
Try this math:
vol = 720G
LUN = 460G
free1 = 260G
snap used = 117G
free2 = 143G
Fractional = 92G (20% of 460G)
free3 = 51G
space used = 460 + 117 + 92 = 669
Hope this helps,