Hi,

newbie to the forum, so not sure where to put this question. Apologies in advance for any etiquette breach..

Q : Does linux have any inherent network throttling ?

Problem: I am using rsync to backup from one linux machine to another. Both machines have Gigabit Cards and it all flows through a Gigabit switch.

When I start the transfer, I get 40-45MB/s which is great, however after about 10mins, the rates starts to drop further and further until we get to around 0.5-1.0 MB/s.

There is no other significant traffic on the network and the both the source & destination machines are busy, but not stretched by any means.

Any thoughts would be appreciated.

I'm not an expert on networking as such, but the situation you describe does not, to me anyhow, sound like a software or network throttling issue. And to my knowledge, there's no "inherent" throttler that would act like your described situation. Maybe iptables could be configured to do rate-limiting, on a time-based scale, but...

Is there any possibility that component temperature could be playing a role here? Do the machines and/or NICs have adequate airflow, and is the switch not locked up in a little stuffy room, or near other warm/hot equipment? This is the first thing that comes to my mind -- temperature.


Sasha

Hey Sasha,

Thanks for your reply..

The machines room (cupboard) is slightly above room temp, but nothing too dramatic. I'll stick a thermometer in there..

As for iptables.. I'll have a route around (sorry.. bad joke).

Could it be to do with Buffering ?

Since posting, I tried something..

I bounced the target and it went back to 40MB/s and then again after a period slowed.

Sooo Frustrating.. I could write a cron to bounce the machine every 20 mins :0)

Tell us more specifics. What commands are you using? When you say bounce, what do you mean? Is one of the machines a desktop or laptop that's going into some sort of sleep mode? What does `top` tell you? How much data are you transferring? How full are the drives on either side?

Hey,

Thanks for your interest in this:

Commands : I'm doing a pull from target with the command :: rsync -avt --progress root@192.168.100.60:/u03/* .

Bounce : Cold start of Target

Machine : they do not sleep.
Source is a Dell Poweredge 1900 (Dual Quad-Core) with 16GB mem (Oracle Linux)
Target is a WhiteBox (Quad-Core) with 8GB (Oracle Linux)

Data Size : Moving a 250GB database. (The largest DB file is 2GB).

Target Drive is 500GB, so will be 50% full (When done)

Top on Target : Tells me that rsync and ssh are chewing cpu (approx 15% between them) Average load is 1.45

Kind Regards
Nomad

Hi

Just to let you know, that this issue is now resolved. We swapped the whitebox out. Runing full wack now. Don't have time to work out what happned to the other box, could have been hardware???, or the linux install??..

Thanks both for your help.

Kind Regards

Nomad

If that whitebox server was running software RAID, or had very low disk speed, that could be the issue... I've seen that pop up on occasion when copying large files from a fast server to an older/slower one.