Oracle has pulled a Scrooge on us, voiding our November order for 320 TB of Thors - before they were discontinued. We didn't make it in time. Now we need to explore options and plans for our disk storage. Also to get us through this particular crunch - we have some 55 TB free at the time of writing, and owe 128 TB to KIPAC and BABAR!
Possible elements of the plan:
- clean up existing space
- explore replacing disks in existing fileservers with 2 TB ones
- find a new vendor(s)
- change storage model
Clean up
We have 1.05 PB of space in xrootd now. Some 640 TB of that is taken up by L1, and 90% of that space is occupied by recon, svac and cal tuples.
Replacing Existing Disks
New Vendors
Two obvious candidates are in use at the Lab now: DDN by LCLS, and Dell el cheapo by ATLAS.
DDN
Dell
These are $160/TB, but low density.
Change Storage Model
The idea is to use HPSS as a storage layer to transparently retrieve xrootd files on demand. Wilko thinks the system can push 30-50 TB/day from tape. This is comparable to the rate needed for a merit reprocessing and so is thought not to be a major impediment. In this model, we would remove the big files from disk after making 2 tape copies. They would be retrieved back into a disk buffer when needed. So we would have a relatively fixed disk buffer, and a growing tape presence.