mhddfs very slow - 25% of disk speed

[Jort]

mhddfs seems unreasonably slow.

Writing to the underlying mountpoints, I get around 322mb/s, writing through mhddfs I get 82mb/s.

Command to write the file: dd if=/dev/zero of=delme bs=10000000 count=1000

This is while there is no other load on the disk (either through mhddfs or directly), and practically no load on the server. 24 Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz CPUs, and the disk is a selection of zfs pools (all give comparable results - the figures above are for a 66 disk pool, with 11 sets of raid-z2 - essentially the same as raid 60).

I tried unmounting and remounting both the mhddfs and the ZFS pools, and it made no difference.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: mhddfs 0.1.39+nmu1ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-92.139-generic 3.13.11-ckt39
Uname: Linux 3.13.0-92-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
ApportVersion: 2.14.1-0ubuntu3.21
Architecture: amd64
Date: Thu Aug 25 09:00:07 2016
InstallationDate: Installed on 2013-08-06 (1114 days ago)
InstallationMedia: Ubuntu-Server 12.04.2 LTS "Precise Pangolin" - Release amd64 (20130214)
ProcEnviron:
 LANGUAGE=en_NZ:en
 TERM=screen
 PATH=(custom, no user)
 LANG=en_NZ.UTF-8
 SHELL=/bin/bash
SourcePackage: mhddfs
UpgradeStatus: Upgraded to trusty on 2016-01-20 (216 days ago)