Re: Strange FTP Transfer Rates

From: Bela Gazdy (bela_at_bluedog.cc.emory.edu)
Date: 03/02/04 

Date: 2 Mar 2004 11:31:08 GMT

Bill <bverzal@komatsuna.com> wrote:
B> Bela Gazdy <bela@bluedog.cc.emory.edu> wrote in message news:<c1niq5$bqd$1@puck.cc.emory.edu>...
>> FTP transfer between two AIX boxen, both at AIX 5100-05 (ftp server v4.1).
>> The NIC is the same, IBM 10/100 Mbps Ethernet PCI Adapter, on both, with
>> 100_Half_Duplex on Box A and 10_Half_Duplex on Box B. Same subnet.
>>
>> I ftp-ed the same, ~4.5 MB file back and forth between A and B. Here are
>> some of the rates I've recorded
>>
>> A -> B B -> A
>> ====== ======
>> 212.8 5009
>>
>> Does anyone have an explanation of 1) the oscillation between two
>> consecutive, identical transfers, and 2) the dependence (difference) of
>> the rates on the direction of transfer?
>>
>> Any idea would be greatly appreciated!

B> Assuming that you are ftp'ing the same file each time:

B> Pass #1, the ftp is reading the file from disk.
B> Pass #2, the ftp is reading the file from the FS cache.

B> I assume this is 4 iterations of different files.

B> CPU speed and architecture will affect speed, as will disk config.
B> When I FTP across my SP switch from the MCA 200MHz node to my S80, it
B> runs at xxx speed. If I go from the S80 to my 200MHz SP node, it goes
B> xxxxxxxx fast.

Thanks Bill!
Okay, cashing makes sense in explaining why two consecutive transfers differs;
however, how would you explain the vast (10x-40x) discrepancy between the same
two machines (p170 and p620) in send vs. receive? FTPing the same file from
the 170 to the 620 is very slow (under 100 Kb/s) while the reverse is
reasonable (over 1000 Kb/s). It does not really matter which machine's ftp
server is used, speed seems to be dependent entirely on direction. Could this be
simply disk I/O-related? The p620 is faster, but not by an order of magnitude. 

-- 
Bela Gazdy, EUCLID/AIX Systems Support

Relevant Pages

  • Re: Anyone interested in another public access system
    ... Bill Gunshannon wrote: ... all over the disk!. ... Fragmentation was an issue. ... VMS Backup. ...
    (comp.os.vms)
  • Re: First-timer buying AS/400 and have questions
    ... (writes memory to disk for the next boot). ... I use the Internet to get PTFs and FTP them to the AS/400. ... IBM was thinking bubble memory or some form of solid-state ... Running FTP from the AS/400 you use NAMEFMT 0 to mean the ...
    (comp.sys.ibm.as400.misc)
  • Re: Slow Filesystem I/O
    ... > Bill Todd wrote: ... >>it onto the disk as compensation, ... Spiralog did not change *default* file system behavior in any ... when RMS specified that its internal buffer should be ...
    (comp.os.vms)
  • Re: Redemption
    ... (despite his admitted assholeness. ... I also feel some kinship with the "target" as you say, ... Bill made a list of things he claims were left here that I would not ... Included in this list was his XP disk. ...
    (alt.gathering.rainbow)
  • Re: Slow network performance
    ... From Linux to Linux (1 ... Also don't forget that Solaris doesn't run with disk write caching ... ftp> put eWA-1_000.zip ...
    (comp.unix.solaris)