On 2013-02-06 06:56, Sorin Srbu wrote:
>> From: Les Mikesell [mailto:lesmikes...@gmail.com]
>> You are testing sustained transfer times there. The killer with small
>> files is the seek time while the disk head bounces around reading
>> little bits of directory and inode data. And once you get started,
>> the server has to do approximately the same to check for matches -
>> possibly with other backups running.
>
> I realized that afterwards. I'll be looking for some kind of random test
> instead.
No, this is what you want:
/usr/bin/time -v find /home -mtime 1 >/dev/null
This will generate a list of all files in /home, checking each of their
modification times, and throw all the output away. This performs a total
directory traversal where each file's inode is checked. This is almost
certainly the limiting factor of your rsync.
The above spits out a lot of output. You are interested in "User time" (CPU
time in userspace) and "Elapsed (wall clock) time". Example from my PC:
tyler@baal:~$ /usr/bin/time -v find /home -mtime 1 >/dev/null
Command being timed: "find /home -mtime 1"
User time (seconds): 0.14
System time (seconds): 0.96
Percent of CPU this job got: 15%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:07.07
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 2320
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 1512
Voluntary context switches: 2398
Involuntary context switches: 196
Swaps: 0
File system inputs: 31000
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
Directory and inode data is cached by the kernel so subsequent runs are
faster. You can tune these with sysctl:
vm.swappiness
vm.vfs_cache_pressure
More information (shameless use of my blog):
http://www.tolaris.com/2008/09/28/making-the-gui-faster-in-ubuntu-linux/
Regards,
Tyler
--
"There is no 'eastern' and 'western' medicine. There's 'medicine' and
then there's 'stuff that has not been proven to work.'"
-- Maki Naro, "The Red Flags of Quackery, v2.0", Sci-ence.org
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