Mail Archives: cygwin/2009/06/29/14:59:58
I scp'd a 1.6 GB file back and forth to a Linux server over GigE to a
fast new RAID-10. I tested 1.7.0-50 and 20090629.
Results:
On a 32-bit XP box, 1.7.0-50 gives about 15 MByte/sec for both upload
and download. (This box can't really hit GigE speeds due to crappy
cabling and a low-quality switch.) On switching to the snapshot, the
download speed is about the same, but upload is cut to 4-5 MB/sec.
On a 64-bit Vista box, 1.7.0-50 gives inconsistent behavior. Download
behaves as it should: ~45 MB/sec here, due to better switch and cabling.
But, uploading with scp gives the reported behavior: the scp status
fills out to 100% very fast but then scp doesn't finish running for
quite a while. It's like it's buffering a big fraction of the 1.6 GB,
which isn't impossible, since this box has 12 GB of RAM. (Core i7,
DDR3, wheee!)
After switching to the snapshot on that Vista-64 box, the scp progress
display becomes useful, growing steadily as scp runs. Unfortunately, my
upload speed is down to around 5 MB/sec here, just as on the XP box.
A different non-Cygwin scp client I have here can manage much faster
transfer speeds, so I can rule out disk and network bottlenecks. The
slowdowns are in Cygwin itself or the Cygwin scp port.
I can rule out a problem in the general network I/O handling: changing
the DLL doesn't seem to affect ttcp results materially. It's either scp
or the way scp uses cygwin1.dll.
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