I am doing some tests with creating and deleting large files in a sles12 installation on our AHV environment. I use an ext4 filesystem and have enabled the trim/discard feature for the filesystem and lvm. But when i delete a large file with random data (5g size) the storage backend of the cluster does not see that the former used storage is now not longer used. I tried fstrim to initiate the cleanup but that doesn´t work. If I write zeros to the file/partition/filesystem then the backend gets backs the storage.
Is trim/discard supported to tell the storage backend that filesystem space is no longer needed or does anybody has experience with such a setup ?
Thank you for your help.
Best answer by Jon
Generally if you're mounting the file system with the discard option, that should be enough.
Keep in mind, when using discard in the guest OS file stystem, the storage will be discarded on the backend as requested, but Prism might not update until the next full curator scan.
This article has some good info on discard in suse OS's: https://en.opensuse.org/SDB:SSD_discard_(trim)_support
Past that, if you are not seeing storage reclaimed after a full curator scan (generally every 6 hours), feel free to open a support ticket and we can dig into it with you. Portal.nutanix.com for NX and SX models, and the respective OEM for Dell XC and Lenovo HX