Hey admin colleagues
1) Do you run CEPH?
2) If so, do you have a SSD backed pool?
3) Do you use this pool for RBD images?
If you've answered all three with yes, do you run fstrim inside these RBD devices? (If yes please leave a comment so we can maybe reach out to you.) If you don't do it for a reason please leave a comment.
@ops yep, but also when I still had HDDs below, as fstrim on an rbd image reduces the number of objects in use - thin provisioning and stuff
Discard for the SSDs below is issued by bluestore already
@LittleFox the performance with HDDs here was too bad and HDDs to cheap.
Do you see major performance issues during the fstrim run on your VMs? How big is your cluster?
@ops most images (again, serving only single applications most of the time) are around 8GiB, but there are some outliers up to 300GiB (which actually serves as VM disk)
Gonna run a fstrim on that big disk now and report wall time and IOPS while it's running
@ops fwiw full fstrim on the 300GiB took 159s with up to 1.5k IOPS reported by ceph - filesystem mixed ext4, xfs and btrfs, with most data on btrfs