Public bug reported:

The outlook:

We deployed Microcloud solution for the client (LXD+Microceph+MicroOVN cluster)
We are testing the perform of CephFS base

The reproduction of this when having cluster established

1. Create LXD VM and attach cephfs volume

sudo lxc launch --vm -c limits.cpu=8 -c limits.memory=8GiB ubuntu:24.04 
test-fio-cephfs -s remote --network=OAM_OVN
sudo lxc storage volume create remote-fs fio-cephfs-test size=1000GiB
sudo lxc config device add test-fio-cephfs cephfs-data disk pool=remote-fs 
source=fio-cephfs-test path=/cephfs

2. then we install fio, git clone the repo repo with testing suite.
cd /cephfs
git clone https://github.com/canonical/ua-reviewkit
cd ua-reviewkit/storage/fio
and run
./run-tests.sh --name mytest --job all --class all --yes


The microclous consists of 3 nodes each:
1.  Intel(R) Xeon(R) Silver 4314 CPU @ 2.40GHz
2. 512GB of RAM
3. 2x960GB in hardware  RAID1 for rootfs
4. 4x 5.8T SAS NVMe disks for microceph

We tested the following scenarios
1. We mount the storage volume as above and run the tests on it
While read speed was ok 991MB/s on 4K randread and 4400MB/s on 4M randread
the write speed was really poor 
1.15MB/s for 4k randrw (write)
and 97.3MB/S for 4m randrw (write), the pure write was similar

2. We tried to improve by changing the logical sector to match physical (4K 
instead 512b) (cluster was redeployed)
A small improvement almost everywhere up to 10%-15%

3. Using the 9p driver on VM instead of virtiofs.  The LXD will use 9p
driver if virtiofs driver is not available (so we blacklisted virtiofs
on vm)

The results are little better for 4k randrw (write) but for other worse

4. Direct mount cephfs filesystem (created by lxd: lxd_cephfs) on the
baremetal host on one of the nodes

Now the write are solid, but read performace is little worse that
initially tested on VM

5. Direct mount cephfs filesystem on VM

The results worse than on baremetal but still pretty good for write

The results were summarized in this table:
https://docs.google.com/spreadsheets/d/1AE_S9TJ2zSSOOo-Bu9Mig_55ciaqjl9CaQ_J27oNCPY/edit?gid=0#gid=0

** Affects: lxd (Ubuntu)
     Importance: Undecided
         Status: New

** Summary changed:

- Poor performance of storage volume with cephfs driver
+ Poor write performance of storage volume with cephfs driver

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https://bugs.launchpad.net/bugs/2112657

Title:
  Poor write performance of storage volume with cephfs driver

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