Network Transfer Anomalies

E

elguapo

Limp Gawd
Joined
Oct 6, 2004
Messages
317
After recently setting up my new server, I have been noticing some data transfer anomalies when backing up some files. I am transferring from by desktop (C2D E6700, 2GB, D975XBX mobo, Intel Pro/1000 onboard gigabit ethernet, Windows XP Pro) to my primary server (Penguin Computing Relion 102, 3.4GHz P4, 2GB memory, dual onboard gigabit nics, 3ware 9550SX Raid card with 4x500GB Seagate 7200.10 16MB drives, SATAII, RAID 5, 128k stripes, running gentoo 2.6.20-r6). The consistency of the files is primarily TV shows and movies, files ranging from 100MB to some 5GB DVD images. There are also some small documents which account for less than 5% of the total that I am transferring, approximately 70GB.

The issue is that the transfer is horribly inconsistent. The speed over the gigabit connection ranges from 25% of the load (about 250mbps) down to less than .1% of the load, (>1mbps). I have no expectations of continuously attaining 250mpbs, but it seems like the speeds are consistently closer to the low end. Heres a graph of some of the transfer.

transfer.jpg


As you can see, there seems to be a burst period of transfer which then quickly drops off to less desirable speeds. Any suggestions?
 
more details:

How are you backing up these files? (Windows Shares, Rsync, SCP, FTP, etc etc)
Are you tarballing them during the process?
 
Mapped network drive, the server is running Samba 3.0.24 Right now i'm thinking that the MTU might not be set properly. The desktop has the MTU set to 9000 (jumbo frames support) but the gentoo box is set to 1500 and I cant change it above that for some reason, I think its a driver lock issue or something. All network devices need to support jumbo frames for it to work, and I just checked and my switch does, so what I need now is to find out how to change the MTU on the gentoo box's NICs above 1500.

and no, no compressing or anything.
 
Do other protocols do the same? Download or upload a big file over http or ftp, and see if you get the same anomalies. Then tune your samba setup if it proves necessary.
 
I am having similar issues. What's even more annoying I can pull at ~200Mbit/s from the Linux server, but push onto it at around 5%. I have tried tuning samba (see my thread) but it did not do any good. According to the samba manual, socket options should not need tweaking in recent kernels. I ran iperf to test the network and it showed results like these:

Code: 
deb-serv:/dev/shm# iperf -f m -c 192.168.3.8 -w 2m
------------------------------------------------------------
Client connecting to 192.168.3.8, TCP port 5001
TCP window size: 0.25 MByte (WARNING: requested 2.00 MByte)
------------------------------------------------------------
[  3] local 192.168.3.16 port 59678 connected with 192.168.3.8 port 5001
[  3]  0.0-10.0 sec  1016 MBytes    852 Mbits/sec
deb-serv:/dev/shm# iperf -f m -s
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 0.08 MByte (default)
------------------------------------------------------------
[  4] local 192.168.3.16 port 5001 connected with 192.168.3.8 port 4544
[  4]  0.0-10.0 sec    911 MBytes    763 Mbits/sec

So I tried U_M's suggestion and installed an FTP server (proftpd, standalone) and used SmartFTP to connect. I can copy a file (down) at 90MB/s (from RAID-5 array, 600MB file), but my upload is limited to ~30KB/s (coincidentally my internet upload speed!?)
 
drizzt81 said:
So I tried U_M's suggestion and installed an FTP server (proftpd, standalone) and used SmartFTP to connect. I can copy a file (down) at 90MB/s (from RAID-5 array, 600MB file), but my upload is limited to ~30KB/s (coincidentally my internet upload speed!?)
Click to expand...
Are you sure your route to that system is through the LAN rather than the internet, then? I would guess not - you're getting 90 MB/s down, and I'd guess your internet is slower than that - but there could be something funky going on with your routing tables. I hate to suggest this - but what happens if you unplug your modem from the network, so you know that's not the cause?

Interesting that you get 50 megabits (right?) to the server with Samba but only 250 kilobits with FTP. Tried any other protocols?
 
unhappy_mage said:
Are you sure your route to that system is through the LAN rather than the internet, then? I would guess not - you're getting 90 MB/s down, and I'd guess your internet is slower than that - but there could be something funky going on with your routing tables. I hate to suggest this - but what happens if you unplug your modem from the network, so you know that's not the cause?
Click to expand...
when I woke up I was planning to try this. Both my debian server and my windows workstation are multi-homed. I did connect to the GbE IP directly, but who knows what smartftp did.
Interesting that you get 50 megabits (right?) to the server with Samba but only 250 kilobits with FTP. Tried any other protocols?
Click to expand...

I noticed that one of my logical volumes on the raid ran out of space when I got up this morning (moving some DVDs) and screwed up the growing process (do not ask), so I had to reboot. Amazingly, now I get up to ~400Megabits/s via samba.

Then I switched my workstation's VMWare Server Network settings around and *boom* back to ~4-5% utilization.

When I get back from working out it's time to see if disconnecting the second adapter does anything.

disconnecting does not do anything.
I now get ~20 Megabits/s via FTP upload, and around 950 Megabits/s download. I changed the routing table and assigned the GbE a lower metric.
 
Tried some samba tuning, SO_RCVBUF=16384 SO_SNDBUF=16384, no change. I'm trying ftp and I'll see if that helps. I'm still not convinced its not jumbo frames though...
 
What about a straight SCP copy?

Grab Bitvise Tunnelier for Windows (it's free, but not GPLed) and copy some stuff to/from your Linux box, let's see how that performs
 
My problem was apparently related to CPU utilization. VMWare + F@H client = crappy GbE transfer rates.
 
unhappy_mage said:
Or WinSCP ;)

Interesting that CPU usage would be so closely tied to performance :p
Click to expand...

using PSCP (from the guys that make PuTTY) I get ~10MB/s while putting (har har the pun ;) ) a file to the server with my VMWare SMP F@H client running. Around 11MB/s without F@H. At the same time, I get around 34MB/s via Samba.
Pulling via SCP yields ~2MB/s. It appears to me that scp is not a protocol suited for high-speed connections?
 
Well drizzt, it's encrypted, too.

I pull about 10MB/sec across a 100mbps LAN at work.....fed by disks much much faster than the 100BaseTX can keep up with.

It's fine for most things, though. I'm not in a hurry (gov't jobs ftw) :)
 
Using SFTP (WinSCP) I can upload to the server at about 6.3MB/s consistently, and download at 2.1MB/s consistently. The spikes are within10% of those numbers and are short lived. It's not a CPU issue. I know that. Its a dual core 3.4GHz P4 and the cpu utilization doesn't go above 0.8% during download or upload.
 
elguapo said:
Using SFTP (WinSCP) I can upload to the server at about 6.3MB/s consistently, and download at 2.1MB/s consistently. The spikes are within10% of those numbers and are short lived. It's not a CPU issue. I know that. Its a dual core 3.4GHz P4 and the cpu utilization doesn't go above 0.8% during download or upload.
Click to expand...

Try an FTP transfer.
 
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