topic Re: scp -pC compression mode. in Operating System - Linux

scp -pC compression mode.

gb karki — Fri, 17 Apr 2009 09:29:30 GMT

Hi Expert,

When i'm coping the 5 GB file to remote location using scp only and where bandwidth link is only 40MB.

I'm enabling compression mode(scp -C), can slow down the server? and will it increase the server load ?

Regards
Karki

Re: scp -pC compression mode.

Pnaidu — Fri, 17 Apr 2009 12:42:19 GMT

Hello Karki,

enabling compression on scp will surely increase the system load, how much will it be taking load, depends on the file size and cpu load.

scp -C will compress the data before sending over to network , Bydefult scp uses 3DES encryption , try using blowfish algorithm which may speed up the transfer, not sure if visibly you can find the difference.

Thanks,

Re: scp -pC compression mode.

Viktor Balogh — Sat, 18 Apr 2009 13:37:54 GMT

hi,

here is some useful information on finetuning ssh.

"Enabling HP-UX Secure Shell to Take Advantage of High Speed Networks"

http://docs.hp.com/en/5991-7493/ch06.html

altough if the data is large i would rather suggest you to copy it over NFS, it is much less CPU-extensive.

Re: scp -pC compression mode.

Steven Schweda — Sat, 18 Apr 2009 20:37:01 GMT

> [...] bandwidth link is only 40MB.

Is that per second? Per year? (If it's per
_job_, then you're in _real_ trouble.)

> [...] can slow down the server?

Many things are possible. Adding data
compression to an existing job will certainly
increase the CPU work. But only a psychic
can know anything about your "server",
because you've certainly told us nothing
about it. My psychic powers are too weak to
tell me whether you will see a slow-down.

Have you considered running some simple
tests? Reality can be much more reliable
than any guesses you might get in this forum.
(Especially when no one here is likely to
have enough information to make a good
guess.)

Re: scp -pC compression mode.

skt_skt — Mon, 20 Apr 2009 14:24:01 GMT

check my thread

http://forums13.itrc.hp.com/service/forums/questionanswer.do?threadId=1144732

Re: scp -pC compression mode.

gb karki — Mon, 20 Apr 2009 14:42:09 GMT

Hi Theyyan,

Thanks for reply.
I have checked with compression mode, this is very much fast but it will increase the CPU utilization.

# scp -pC hrp.fbackup 10.108.129.12:/tmp/

Password:

hrp.fbackup 100% 1763MB 1.0MB/s 15.4MB/s 28:10

#top

CPU TTY PID USERNAME PRI NI SIZE RES STATE TIME %WCPU %CPU COMMAND

0 pts/1 2733 root 154 20 17632K 3700K sleep 0:44 52.97 52.32 ssh

# scp -p hrp.fbackup 10.108.129.12:/var/

Password:

hrp.fbackup 100% 1763MB 480.3KB/s 1.4MB/s 1:02:38

#top

CPU TTY PID USERNAME PRI NI SIZE RES STATE TIME %WCPU %CPU COMMAND

6 pts/1 1349 root 154 20 16096K 2164K sleep 0:29 2.23 2.22 ssh

Regards
Karki

Re: scp -pC compression mode.

mohamed.bouraoui — Fri, 24 Apr 2009 09:43:55 GMT

Be careful, some compress method donâ t support more than 2 gb file by filesystem.
Man scp can you help .
Good luck