allocsize mount option

[Peter Vajgel]

We write about 100 100GB files into a single 10TB volume with xfs. We are using allocsize=1g to limit the fragmentation with a great success. We also need to reserve some space (~200GB) on each filesystem for processing the files and writing new versions of the files. Once we have only 200GB available we stop writing to the files. However with allocsize it's not that easy - we see +/- 100GB added or taken depending if there are still writes going and if the file was reopened ... Is there a way to programmatically disable allocsize speculative preallocation once we exceed certain threshold and also return the current speculative preallocation back to the free space (without closing the file)?

Thx

Peter Vajgel