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On 1/31/2011 12:10 PM, Jim Lawson wrote:
>
>
> On 1/31/11 11:25 , Helen Read wrote:
>> I brought this up on the list a while ago, and it is still an ongoing
>> problem. Accessing files on a mapped network drive over the VPN from
>> home is extremely slow. It takes a very long time even to select files
>> (so as to copy them to a local folder). Once they are selected, the
>> files copy quickly, but it takes forever to get them selected, to the
>> point of Windows Explorer not responding. Opening files directly on
>> the mapped drive is also incredibly slow and results in whatever
>> application that is trying to open the file (Mathematica, Excel, Word)
>> Not Responding.
>>
> The VPN provides communications security, but there is a tradeoff.  It
> reduces bandwidth, and increases latency.   This is something of a pat
> answer, but CIFS (the protocol that's used when Windows maps a drive),
> in spite of its name, does not perform all that well when there is low
> bandwidth, high latency, or packet loss.  If you were already connecting
> through a "long thin pipe", as it were, the VPN is only going to make
> that worse.
>
> You might have better luck using SCP or SFTP from home.  The interface
> may not be as convenient, but I think you will find it faster for copy
> operations.  An added bonus is that using SCP or SFTP does not require
> the use of the VPN.  You can download WinSCP from www.uvm.edu/software.

I cannot for example access the Math Department web space over SFTP, 
only via a mapped drive. And SFTP is just a huge pain in the neck 
generally (I lived with it all those years until I finally got broadband 
in my neighborhood a few months ago).

Is there no way to make the mapped drives work better over VPN? I swear, 
it didn't used to be like this when I mapped drives on the VPN when 
travelling (when I still had dial-up at home).

And it's not entirely limited to the VPN. Many people in my department, 
including me, have had problems for the last several months with extreme 
slowness opening up files from mapped drives on campus, without VPN.


>> And now, I have an even worse problem. Files that my students submit
>> (via a secure webpage requiring NetID login) end up in a directory in
>> my public_html directory on Zoo. Over the weekend, I copied the files
>> to a local directory so that I could open them and grade them (very
>> sloooow to select them for copying, as usual). Two files were
>> completely corrupted (in different ways). I e-mailed the students and
>> asked them to open up their file to make sure it was OK (these are
>> Mathematica .nb files, which are actually ASCII) and resubmit it. Both
>> of them said that their files were fine at their end, and resubmitted.
>> I copied the newly submitted files to a local directory, and both were
>> corrupted in the same way as before for each respective student (but
>> different from each other). One of the students submitted a third
>> time, with the same result. So this morning, at my office, I opened up
>> all five of these files from the mapped network drive, no VPN, and lo
>> and behold all five files are perfectly fine.
> I have never seen CIFS *corrupt* a file.  Is it possible that the files
> were only partially transferred to your home computer?

It was files only from these two particular students, and it happened 
again when they resubmitted. All the other files were fine, and there 
wasn't anything unusual that I can see about the ones that got 
corrupted. They were not large, for example.


-- 
HPR