While building out a demo environment I had cause to thin-provision already thin-provisioned storage (that might be on a thin-provisioned array. Don’t try this in production!)
The issue was a pre-configured LeftHand P4000 appliance providing iSCSI LUNs to nested ESXi hosts, and needing to present 1.5TB worth of LUNs on an appliance that only has 120GB total and 80GB available.
I needed to create the additional LUNs without affecting the existing LUNs and ensure that one LUN filling up won’t kill all of the LUNs.
Step one is creating the new LUN (called a “volume” in the LeftHand GUI) and then locating the “Thin” setting on the advanced tab.
Once the new LUNs are created, I wanted to be sure that someone filling up one would not affect the others. Without some guarantee of space, if someone wrote 80GB to the 1TB LUN no other thin provisioned LUN could be written to. Enter the commandline “CLIQ”
The command modifyVolume name=volumename reserveQuote=size will set a minimum threshhold for that LUN. It defaults to 512MB and I want to adjust it so that at least 20GB can be written to it. Don’t forget to include the size after the numberic (GB/MB/KB)
So : modifyvolume volumename=LUN6 reservequota=20GB
sets my new thin provisioned LUN6 volume to have at least 20GB reserved for writes. Repeat for all thin LUNs to ensure each has some writable space.
