On 31 dec 2008, at 08:53, Bernard Dugas <bern...@dugas-family.org> wrote:

Wojciech Puchar wrote:

nfsserver# time tar -cf - clientusr-amd64 > /dev/null
5.001u 12.147s 1:23.92 20.4%    69+1369k 163345+0io 0pf+0w

client9# time tar -cf - /usr > /dev/null
tar: Removing leading '/' from member names
3.985u 19.779s 4:32.47 8.7%     74+1457k 0+0io 0pf+0w

Note : clientusr-amd64 is around 1.3GB and is the same directory exported to client9 /usr with nfs.

it's FAST. what's wrong?

First thing that may be wrong is the understanding of the time figures. The documentation is not clear about them and the -h option is not working :

client6# time -h tar -cf - /usr > /dev/null
-h: Command not found.
0.000u 0.000s 0:00.00 0.0%      0+0k 0+0io 0pf+0w

The main thing is that the 3rd figures 1:23.92 and 4:32.47 seems to be the time i wait in front of the computer while it works (ok, i know, i should enjoy a beer, or hot coffee with this nice snow ;-) :

client9# date ; time tar -cf - /usr > /dev/null ; date ;
Wed Dec 31 08:23:59 CET 2008
tar: Removing leading '/' from member names
4.103u 19.651s 4:25.80 8.9%     74+1453k 0+0io 2pf+0w
Wed Dec 31 08:28:25 CET 2008

and 08:28:25 - 08:23:59 = 00:04:26 is very close to 4:25.80.

On server, it means : 1440MB / 84s = 17MB/s
On client, that becomes : 1440MB / 266s = 5.4MB/s

I know the disk is not very fast, but i would like the NFS layer not to add too much...

I don't want my users to wait between 3 or 4 times more because computer is using NFS.

In my opinion there are more considerations than only nfs: the data is pulled twice over the network, and the tar process might initiate paging which is done over the network as well. The tar comparison is not a good one.

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