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Slow file transfer

Posted on 2011-09-14
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Last Modified: 2012-05-12
I am transferring a 1gb file using FTP and the link is 1gb but it is taking over 5 minutes to transfer.

In wireshark I opened the expert infos composite window.

In the experts infos:

I have no errors

I have these warnings:

Window is full   20

Zero Window   17

ACKed lost segment (common at capture start)  63

Previous segment los (common st caputre start)  78

Out-Of-Order segment   187

Fast retransmission (suspected)  14

This was on a 1gb ftp file transfer

The IO graph Y axis shows 50000 when set to auto and the graph varies around 30000

In the notes I have Duplicate ACK (#41) for FTP an FTP data packet

I am trying to narrow down to network or server problem.
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Question by:Dragon0x40
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18 Comments
 
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Accepted Solution

by:
noci earned 167 total points
ID: 36542721
1GB [Byte] + transfer overhead = ~10Gb [bit]
10Gb / 300 s => ~33Mbps  = ~33000Kbps.

If that is slow or not is to be seen. In the equation is also DISK READ at the source, DISK WRITE at the target.
i.e. IMHO not too bad.

If you want to test you need testing tools, those generate traffic without O/S overhead, disk overhead etc.
Prefereably with a range of packet size to excersize various parts of the network between two systems.

NETIO is a nice tool that can handle traffic on Unix, Linux, OpenVMS, Windows....
 http://www.ars.de/ars/ars.nsf/docs/netio

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LVL 16

Expert Comment

by:SteveJ
ID: 36543502
Google "iperf" and you can use that little client / server apo to tune buffers

Good luck,
Steve
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Expert Comment

by:giltjr
ID: 36544879
Are you 100% sure that the full path is a 1Gbps path.  That is, both the client, the server, and all network connections in between.

Are they both on the same subnet or different subnets?

If different subnets, what type of router are you using?

What is the link utilization on all of the links between the client and the server?

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Assisted Solution

by:Gerald Connolly
Gerald Connolly earned 333 total points
ID: 36549283
You are unlikey to get a single stream FTP service to run at anything like 1Gigabit and as @noci pointed out you seem to be mixing your bits and bytes, Its a de facto standard that "b" is bits and "B" is bytes.

so a 1Gbit/sec link is really a 100MByte/sec pipe and you will struggle to get even 50% of that single stream although i think you should get better than 33Mb/s (4MBytes/sec).
Do you have jumbo frames switched on and what is it writing to? a single disk or a RAIDset?
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Expert Comment

by:noci
ID: 36549631
And if there are 100Mbps components are in the loop then are they auto configure port connected to a  non-negotiate port?
In that case you may end up with  HALF/FULL DUPLEX ....
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Author Comment

by:Dragon0x40
ID: 36555519
Sorry about mixing up bytes and bits. bytes are used for disk capacity and files size and bits are used for data transfer.

I think a 1gb/per second link would 125mB/per second? bytes = bits/8 ?

We have transferred the same file to different end points through a layer 2 cloud and this particular location takes about twice or three times as long to transfer the same file as compared to all the other end point locations.
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Assisted Solution

by:Gerald Connolly
Gerald Connolly earned 333 total points
ID: 36555703
1Gb/s = 125MB/s, yes you might think that.

But whenever data gets put onto a comms link you have to account for all the extra protocol which usually works out at 10 bits per byte.
So it is generally accepted that 1Gb/s = 100MB/s


So have you checked (and double-checked) that all the sectors of the link are running at 1Gb/s?
Try other cables.
Use link test software to measure the end-2-end link speed (removes target node disk write overhead)
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Expert Comment

by:noci
ID: 36556433
Additional, the 10 bits per byte ratio only is for relatively large packets.
There is also various delays in drivers, disks, applications ... which slowdown your connections because they add up when applied serially,
There isn't a lot of software that copies data in parallel for one big file.
Also all packets need to be ack'ed after a while so if the receiver  side is slow, the sender will slow down too.
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Expert Comment

by:noci
ID: 36556436
I forgot to mention that you assume there is NO other network activity on the same path you use, and also no other  disk activity at BOTH sender & receiver, and that there is sufficient CPU compute time available  on all equipment involved.
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Expert Comment

by:Gerald Connolly
ID: 36557274
@noci i agree, its just simpler to do the 10 bits per byte

and good point on network activity!
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Expert Comment

by:noci
ID: 36557362
@connollyg,  File transfers mostly are, but telnet traffic has a dramatic overhead (32byte of IP packet + 14 bytes of ethernet  for 1 or 2 bytes of data).


Also the bandwidth of disks can be very low. Depending on USB1.0, USB2.0 or USB3.0 / SATA / SCSI1, SCSI2, SCSI3..
On the writing end there is also the overhead of allocating additional data blocks as the transfer progresses, which can be heavy on fragmented disks...

Any way filetransfers are a not very well adjusted instrument for network performance measurement.
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Expert Comment

by:Gerald Connolly
ID: 36557469
@noci whatever the overhead he should be getting better than 33Mb/sec down a 1Gb/sec link

@noci re disk speeds that why i recomended using a network link test to remove the disk write element from the equation.
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Expert Comment

by:noci
ID: 36558765
@connollyg, see netio in the first answer....
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Expert Comment

by:giltjr
ID: 36559434
Assuming you are running Windows, from one of the computers you are testing with can you provide the output from the command:

     pathping -n x.x.x.x

where x.x.x.x is the IP address of the of the other computer you are testing with?
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LVL 17

Expert Comment

by:rochey2009
ID: 36563201
Hi,

Wireshark has suggested that you have a TCP windowing problem. This means that the sender cannot send anymore data until it receives a TCP acknowledgement. Are you using TCP windows scaling?
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LVL 39

Expert Comment

by:noci
ID: 36563302
@rochey2009, that is also consistent with slowness in the target disks, filesystem overhead, file growth...

So besides network stuff you need info about the disks, bandwidth, seek times, fragmentation....
0
 

Author Comment

by:Dragon0x40
ID: 36915081
I think this may be a routing issue. With extra hops thru the cloud. But great answers! I will post when I find out.
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Author Closing Comment

by:Dragon0x40
ID: 36983523
The next hop in the routing table was incorrect and was sending traffice across the mpls cloud twice.
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