filesytem create times out when pool is based on newly created RAID 5 md device

[trgill]

# mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd
mdadm: layout defaults to left-symmetric
mdadm: layout defaults to left-symmetric
mdadm: chunk size defaults to 512K
mdadm: size set to 585930240K
mdadm: automatically enabling write-intent bitmap on large array
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.
# cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid5 sdd[3] sdc[1] sdb[0]
      1171860480 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/2] [UU_]
      [>....................]  recovery =  0.4% (2344404/585930240) finish=49.7min speed=195368K/sec
      bitmap: 0/5 pages [0KB], 65536KB chunk

unused devices: <none>
# stratis pool create p1 /dev/md0
# stratis filesystem create p1 fs1
Execution failure caused by:
Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.
    which in turn caused:
Error while invoking method "CreateFilesystems" belonging to interface "org.storage.stratis1.pool" with arguments (dbus.Array([dbus.String('fs1')], signature=dbus.Signature('s')))

# cat /proc/mdstat 
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid5 sdd[3] sdc[1] sdb[0]
      1171860480 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/2] [UU_]
      [=>...................]  recovery =  6.7% (39456352/585930240) finish=45.6min speed=199518K/sec
      bitmap: 1/5 pages [4KB], 65536KB chunk

unused devices: <none>

The filesystem gets created - but stratisd is unresponsive during the filesystem create. It creates a confusing situation for a user.

[mulkieran]

This is likely to happen if the max_sync_speed (throughput) is a large part of the capacity of the drives. In that case, the array will devote all its capacity to syncing, and have little left to right the XFS metadata, resulting in long creation times. The storage administrator could reduce the max_sync_speed of the array if intening to do operations on the newly setup pool, a likely scenario.