[tahoe-dev] [tahoe-lafs] #1189: investigate best FUSE+sshfs options to use for performance and correctness of SFTP via sshfs

[tahoe-lafs]

#1189: investigate best FUSE+sshfs options to use for performance and correctness
of SFTP via sshfs
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     Reporter:  davidsarah     |       Owner:                             
         Type:  defect         |      Status:  new                        
     Priority:  major          |   Milestone:  undecided                  
    Component:  code-frontend  |     Version:  1.8β                       
   Resolution:                 |    Keywords:  sftp sshfs performance docs
Launchpad Bug:                 |  
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Comment (by bj0):

 I started doing a couple random tests I could think of.  I didn't repeat
 many of the tests, since they took a bit of time and it's all manual, but
 it sort of gives an idea:

 Most of these tests were copying a large file (728MB .iso file) to and
 from a tahoe introducer/storage client running inside a VirtualBox VM on
 the same host (both guest and host running ubuntu).  Most of the copying
 was done with "time rsync -rhPa ", and when copying a large file to tahoe,
 after the transfer the command hangs for another minute or so.  I checked
 the flog during this time and there was activity (read i think) so it may
 be that rsync tries to checksum the file after transfer, i'm not sure.

 To verify the file was being transfered correctly, I also did "time md5sum
 mnt/iso".  I would expect this to be similar to simply reading the file,
 but for some reason it performed differently...

 '''with it mounted as: "sshfs -p PORT server:/ mnt/"'''
 * rsync .iso TO tahoe:    4m51s to transfer ( 2.39 MB/s ), 6m14s total
 * rsync .iso FROM tahoe:  5m42s ( 2.13 MB/s )
 * cp .iso FROM tahoe: 5m31s
 * time md5sum iso:
    * first try: 7m46s
    * second try: 5m13s

 '''with it mounted as: "sshfs -p PORT -o direct_io,big_writes server:/
 mnt/"'''
 * rsync .iso TO tahoe:    3m37s to transfer ( 3.19 MB/s ), 5m1s total
 * rsync .iso FROM tahoe:  5m15s ( 2.31 MB/s )
 * cp .iso FROM tahoe: 5m31s
 * time md5sum iso:
    * first try: 10m40s
    * second try: 9m25s


 obviously I expect the values to fluctuate a bit, but it seems like
 direct_io,big_writes bumps up the write speed a bit, without really
 affecting the read speed.  I'm not really sure why it hit md5sum time so
 bad...



 I also tried to rsync a large directory of source files (4mb, 981 files)
 to tahoe, but it seems to be acting odd, and stalls a lot, resulting in a
 very long transfer time (120 - 140 minutes).  This happened with and
 without the options.

-- 
Ticket URL: <http://tahoe-lafs.org/trac/tahoe-lafs/ticket/1189#comment:1>
tahoe-lafs <http://tahoe-lafs.org>
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