I am doing backups and restores to and from a backup server machine in the garage (in case of fire or theft) using rsync, and the LAN is running much slower than I think it should.

Best consistent speed I get is 40Mb/s. The lights on the interface cards indicate it's in Gb mode, and the interfaces are fairly new. The router is a Netgear WNDR3700 the top-of-the-line consumer-grade router.

Hardwire only, using Ubiquiti ToughCable and ToughConnectors, less than a 50' run.

What can I look for?

That sounds about right. Unless you are running SSDs or a performance oriented RAID configuration on both sides of the connection, the bottleneck will likely be the hard drives. Rsync is doing a lot of seeking and occasional transfer (after the initial sync), which impacts the transfer rate considerably.

You can do some tuning. You don't mention using jumbo frames - setting the MTU on the interfaces to greater than 1500, if supported by your hardware. That can significantly improve long transfers.

0 members found this post helpful.

Hi,

macemoneta's reply sounds correct.

You could do a few test (expensive local read/writes) and monitor with the iostat command.

Example: check 10 times, every 2 seconds and show in Mb's

Hope this helps.

iperf is a good tool for testing LAN performance. It is cross platform and tests memory to memory data transfer via TCP or UDP. This takes storage speed out of the equation, allowing you to verify your LAN performance.

Could test also with some other file transfer if you think the fault is rsync. Just get a big file of some kind and transfer it ftp maybe.

iperf is not available in Debian, and unfortunately Sourceforge won't let me look at anything without being signed in. I tried the three usernames and password I've used for the past ten years and it refuses them all. I tried to register anew, and it said, "Oh snap! We can't process this request." So I give up on that.

I do notice though that the CPU on the backup server is running rsync at 100% on one core, and very little on the other. It appears that rsync is not multithreaded and this may be my problem. Any idea why, or what can be done about it?

Disks aren't too busy.

dont settle for 40MiB/Sec. a straight jump that wide should be able to hover around 80MiB/Sec. I have a Freenas box / good GB switch, and new motherboards at both ends and it flies!

unrelated: I have to disable/enable the nic on my client to get it "awake" and running healthy again. at least once a day this happens.

edit: ahci mode hard drives help drastically

I would take a hard look at the hard drive activity during big transfers, often the controller/hard drive is the primary bottleneck in this situation.

after you fix rsync so that it can handle 1GiB/Sec, move on to the other things I mentioned (and the FTP test mentioned earlier becassuse FTP has nearly no overhead like rsync)

Errrr, are you sure?

From http://www.debianhelp.co.uk/networktools1.htm -


Install iperf in debian

#apt-get install iperf

CodeKrash, it appears that the CPU on my backup server is maxed on one core with rsync, if top isn't lying. Since rsync is not multi-thread that's the limiting factor. iotop shows on the backup server a read rate from 3 to 7 M/s, and on the destination an average write rate of 4.5 M/s. Both sides are WD Green 2TB drives capable of much more than this. I only see periodic flashes on both machines' drives. I'm pretty sure I'm CPU-bound on the source, one core.

Baldy I tried that before and it couldn't find iperf, even with apt-cache search, but I tried it just now and it installed. Ghosts, I guess.

Ouch!
you may have to add the repository for iperf to apt, I know that with yum this happens often to find some software.
I hope you don't settle for that magnitude of inefficiency.

I was told on the rsync listserv that it's spending time doing file deltas and compression. Recommendation was to change --compress to --whole-file, and in fact that increased my speed from 4.5Mb/s to 18.5!

Much better. Still core-bound though. (not disk, or network)

OK now that I've finished my restore, I've run iperf.
Droog --> Hex 937 Mbits/sec!
Merlin --> Hex 40.6 Mbits/sec (wifi)

So I'm getting amazing performance from the Gb connexion; I should because I used expensive Ubiquiti ToughCable and ToughConnectors for the 70' run to the garage where my backup server is. BTW, Ubiquity has some amazing products, especially the NanoBridge M2.

My wifi performance is not too good, considering that I run 5GHz only, 802.11n. It's a Netgear WNDR3700 router and the client card is the Intel 4595 built into my HP 8710w laptop.

glad to hear it. that's a pretty long run, sounds fun