Dear Janne, I'm concerned with the potential increased NVME wear. Assuming writes of multiples of the block size, when I write 1GB of data to the CephFS, how much data is written to the disks? Best wishes, Manuel On Mon, Jan 30, 2023 at 2:25 PM Janne Johansson <icepic.dz@gmail.com> wrote:
is there information available anywhere about the write amplification for CephFS? I found quite some material on write amplification of VMs using journaled file system on top of RBD but nothing as it relates to CephFS?
From my understanding I would expect the following:
- for X-rep, data needs to be written to X pgs (factor X) - for k-m EC, data is written to k+m pgs (factor (k+m)/k)
Am I correct?
Yes, but in the EC case, far smaller amounts of data will be sent to each PG, so it depends on if you are calculating "amplification" in terms of IOPS or in terms of MBytes (that needs to be sent over the network and written to disk).
-- May the most significant bit of your life be positive.