[Gluster-users] Performance question

[Joe Julian]

I'm using an unpatched fuse 2.7.4-1 and glusterfs 2.0.2-1 with the 
following configs and have this result which surprised me:

# dd if=/dev/zero of=foo bs=512k count=1024
1024+0 records in
1024+0 records out
536870912 bytes (537 MB) copied, 14.1538 seconds, 37.9 MB/s
# dd if=/dev/zero of=foo bs=512k count=1024
1024+0 records in
1024+0 records out
536870912 bytes (537 MB) copied, 24.4553 seconds, 22.0 MB/s

Why is it slower if the file exists? Should it be?


#############
Servers
#############
volume posix0
  type storage/posix
  option directory /cluster/0
end-volume

volume locks0
  type features/locks
  subvolumes posix0
end-volume

volume brick0
  type performance/io-threads
  option thread-count 8
  subvolumes locks0
end-volume

volume posix1
  type storage/posix
  option directory /cluster/1
end-volume

volume locks1
  type features/locks
  subvolumes posix1
end-volume

volume brick1
  type performance/io-threads
  option thread-count 8
  subvolumes locks1
end-volume

volume posix2
  type storage/posix
  option directory /cluster/2
end-volume

volume locks2
  type features/locks
  subvolumes posix2
end-volume

volume brick2
  type performance/io-threads
  option thread-count 8
  subvolumes locks2
end-volume

volume posix3
  type storage/posix
  option directory /cluster/3
end-volume

volume locks3
  type features/locks
  subvolumes posix3
end-volume

volume brick3
  type performance/io-threads
  option thread-count 8
  subvolumes locks3
end-volume

volume server
  type protocol/server
  option transport-type tcp
  subvolumes brick0 brick1 brick2 brick3
  option auth.addr.brick0.allow *
  option auth.addr.brick1.allow *
  option auth.addr.brick2.allow *
  option auth.addr.brick3.allow *
end-volume

################
Client
################
volume ewcs2_cluster0
  type protocol/client
  option transport-type tcp
  option remote-host ewcs2.ewcs.com
  option remote-subvolume brick0
end-volume
volume ewcs2_cluster1
  type protocol/client
  option transport-type tcp
  option remote-host ewcs2.ewcs.com
  option remote-subvolume brick1
end-volume
volume ewcs2_cluster2
  type protocol/client
  option transport-type tcp
  option remote-host ewcs2.ewcs.com
  option remote-subvolume brick2
end-volume
volume ewcs2_cluster3
  type protocol/client
  option transport-type tcp
  option remote-host ewcs2.ewcs.com
  option remote-subvolume brick3
end-volume

volume ewcs4_cluster0
  type protocol/client
  option transport-type tcp
  option remote-host ewcs4.ewcs.com
  option remote-subvolume brick0
end-volume
volume ewcs4_cluster1
  type protocol/client
  option transport-type tcp
  option remote-host ewcs4.ewcs.com
  option remote-subvolume brick1
end-volume
volume ewcs4_cluster2
  type protocol/client
  option transport-type tcp
  option remote-host ewcs4.ewcs.com
  option remote-subvolume brick2
end-volume
volume ewcs4_cluster3
  type protocol/client
  option transport-type tcp
  option remote-host ewcs4.ewcs.com
  option remote-subvolume brick3
end-volume

volume ewcs7_cluster0
  type protocol/client
  option transport-type tcp
  option remote-host ewcs7.ewcs.com
  option remote-subvolume brick0
end-volume
volume ewcs7_cluster1
  type protocol/client
  option transport-type tcp
  option remote-host ewcs7.ewcs.com
  option remote-subvolume brick1
end-volume
volume ewcs7_cluster2
  type protocol/client
  option transport-type tcp
  option remote-host ewcs7.ewcs.com
  option remote-subvolume brick2
end-volume
volume ewcs7_cluster3
  type protocol/client
  option transport-type tcp
  option remote-host ewcs7.ewcs.com
  option remote-subvolume brick3
end-volume

volume repl1
  type cluster/replicate
  subvolumes ewcs2_cluster0 ewcs4_cluster0 ewcs7_cluster0
end-volume

volume repl2
  type cluster/replicate
  subvolumes ewcs2_cluster1 ewcs4_cluster1 ewcs7_cluster1
end-volume

volume repl3
  type cluster/replicate
  subvolumes ewcs2_cluster2 ewcs4_cluster2 ewcs7_cluster2
end-volume

volume repl4
  type cluster/replicate
  subvolumes ewcs2_cluster3 ewcs4_cluster3 ewcs7_cluster3
end-volume

volume distribute
  type cluster/distribute
  subvolumes repl1 repl2 repl3 repl4
end-volume

volume writebehind
  type performance/write-behind
  option aggregate-size 128KB
  option cache-size 1MB
  subvolumes distribute
end-volume

volume ioc
  type performance/io-cache
  option cache-size 512MB
  subvolumes writebehind
end-volume

#######################

mount -t glusterfs /etc/glusterfs/glusterfs-client.vol /mnt/gluster