Poor SMB write speeds

phillxnet · May 3, 2019, 8:25pm

@lexxa Thanks for the update and glad you got it sorted.

Running balances can affect performance but that is definitely more the case once there are more snapshots, however upstream btrfs has made some major improvements in that area so we should get them in time. Plus we have some inefficiencies that have been mostly removed in a pending pull request that should improve our end responsiveness wise (due in 3.9.2-49), but only really a problem when slow downs are in effect.

You might want to keep in mind that when Rockstor convert balances it is rather opinionated with it’s data / metadata levels. I.e. we enforce set metadata raid levels according to the data raid levels. It helps with keeping things flexible and avoiding complicated corner cases such as raid1 metadata not allowing a ‘single’ data level to reduce below 2 disks: where as the expectation in that case is that if the pool is single it can be shrunk to a single drive. Just a though as if you specifically wanted raid1 metadata on multi disk data single pool you may want to appreciate that it might not, after a balance, be the same metadata raid level.

The associated code is:

github.com

rockstor/rockstor-core/blob/master/src/rockstor/fs/btrfs.py#L1509-L1529


      
                  # No need to scan output as nothing to see with quotas disabled.
                  # And since no quota capability can be enacted we return True
                  # to avoid our caller trying any further with quotas.
                  return True
              # otherwise we raise an exception as normal
              raise e
          for l in o:
              fields = l.split()
              if (
                  len(fields) > 3
                  and fields[0] == qid
                  and
                  # Account for potential parent-child column inversion by
                  # checking both parent & child columns for parent qgroup match.
                  # Fixed upstream but observed in distro released btrfs-progs:
                  # see: https://github.com/kdave/btrfs-progs/issues/129
                  # Acknowledged correct:
                  # [0]               [1]         [2]     [3]     [4]
                  # qgroupid         rfer         excl parent  child
                  # 0/340        16.00KiB     16.00KiB 2015/2  ---
                  # 2015/2       16.00KiB     16.00KiB ---     0/340

which is called by:

github.com

rockstor/rockstor-core/blob/master/src/rockstor/storageadmin/views/pool.py#L270-L279


      
                          remount(m, mnt_options)
                      except Exception as e:
                          logger.exception(e)
                          failed_remounts.append(m)
          if len(failed_remounts) > 0:
              e_msg = (
                  "Failed to remount the following mounts.\n {}.\n "
                  "Try again or do the following as root (may cause "
                  "downtime):\n1. systemctl stop rockstor.\n"
                  "2. unmount manually.\n"

There are plans to surface in the Web-UI the metadata raid level also and hopefully, in time, also allow specifying the metadata raid level independently. This would be nice for such things as raid6 data and raid1 metadata (once the parity raids are better anyway), but currently we hard wire metadata levels according to data levels.

Hope that doesn’t spoil your plans, it’s just with so much flexibility in btrfs itself we have to simplify / abridge some what. At least in this stage of our development.

You may also be interested in a recent posting re the current status of our update channels: see the Intro section of:

Hope that helps.