Red Hat Bugzilla – Bug 8656
[Bug 4689] slow network transfer using tar to remote host
Last modified: 2008-05-01 11:37:53 EDT
On 01/13/00 22:44 email@example.com wrote:
> +we never were able to duplicate this. If you are still having problems,
> or the
> +problem was not solved in 6.1, please reopen the bug.
I want to reopen this bug. It has not gone away with 6.1.
I found a way to demo this problem without need of a tape drive. We
have two systems here, named pascal and sobolev. Both are Compaq
Deskpros with CPU >= 300 MHz, running RedHat 6.1. They are connected
via Netelligent 10/100 TX (tlan) network interfaces, to a LAN via CAT5
UTP (10base-T), so neither cpu nor network bandwidth are problems.
They share account information via NIS.
1) /u/pascal that is local to pascal and NFS mounted by sobolev.
A suitably large subdirectory foo (25 MB) is located in this
filesystem, and is to be backed up onto a file on sobolev.
2) /tmp is local to sobolev, and is to receive the backup file.
The procedures below are executed as a normal user with an account on
both hosts, and permission to run r-commands on sobolev (e.g. via
the .rhosts mechanism).
Logged in on host pascal, chdir to local filesystem /u/pascal.
pascal:/u/pascal/$ time tar cf sobolev:/tmp/remote.tar foo
0.750u 2.350s 1:11.49 4.3% 0+0k 0+0io 7433pf+0w
On host sobolev, chdir to the NFS filesystem pascal:/u/pascal.
sobolev:/u/pascal/$ time tar cf /tmp/nfs.tar foo
0.320u 2.990s 0:37.12 8.9% 0+0k 0+0io 187pf+0w
sobolev:/u/pascal/$ ls -l /tmp/*.tar
-rw-r--r-- 1 moniot staff 25937920 Jan 14 12:17 /tmp/nfs.tar
--w---xr-- 1 moniot staff 25937920 Jan 14 12:15 /tmp/remote.tar*
Do the math:
Slow method: 26 MB/ 71 s = 370 KB/s
Fast method: 26 MB/ 37 s = 700 KB/s
The numbers vary a bit depending on system and network load, but the
basic difference remains. With the tape drive we are seeing a bigger
difference (a factor of 3 to 4), but that seems to be due to the tape
drive being on an alpha-OSF system.
(The permissions of remote.tar look a bit odd too, now that I notice
them. But never mind that now.)
Fordham University email: firstname.lastname@example.org
Fordham College Lincoln Center URL: http://www.dsm.fordham.edu/~moniot/
New York, NY 10023 phone: (212) 636-6311
jeff or bero: do you have time to investigate this?
Not today (config tool freeze) - maybe later.
Bero: please investigate.
This is normal NFS overhead in the way tar works (opening a series of small
files over nfs has a lot of overhead); can't be fixed.