1000+ file transfer

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1000+ file transfer

Postby sjpete » Thu May 20, 2010 9:59 pm

Seems this question is raised a few times, but no answers.

Writing a lot of (small, < 10kbyte) files, system goes to 50kByte/second average. On the bandwidth meter, it pulses every 10-15 seconds 10 500kbyte/sec for a few seconds, and than back to zero. That tells me it is NOT a network problem. Can send screenshots of BW meter if needed.

Did change MTU to 1492, no jumbo. Writing large files works OK, IOMeter results are as expected.

It is used as backup for a lot of source code files, but taking more than an hour to transfer a few 1000 files for backup is simply not acceptable.

On the same network PC<->PC transfer goes as expected, again indicating it is NOT a network problem.

Who can shine any light in this. If I don't get it resolved, I'll need to return the unit.

Thanks,
Pete

XP SP2, ReadyNas Duo 2*1T, 4.1.6 SW version, SMART of drives OK
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Re: 1000+ file transfer

Postby WhoCares? » Fri May 21, 2010 6:52 am

You could be running into a file handle issue but I have to admit that's mostly guesswork on my side. I see some similar behavior when unpacking large zip archives. That will go lightning fast for a while, then halt for a few seconds and then continue again. There may be two things at work here.

The first is that the ReadyNAS tries to keep as much stuff in memory as possible so it can serve the contents without needing to get it from the hard drives first. Thus it may happen that memory fills up to the point where the OS says "enough is enough, we're going to write that stuff NOW". Also, the ReadyNAS per default setup is(was? I'd have to check this) limited to 1024 available file handles. Since you're copying rather small files there's a chance you hit the file handle limit before you top out on memory. Even so, to free up some file handles the OS may again decide to first write out everything to disk before it serves new handles to the requesting tasks.

I believe I've seen Chewbacca here on the forums offer a file handle fix for the Pro, maybe there's something similar available for the Duo.

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Re: 1000+ file transfer

Postby sjpete » Fri May 21, 2010 9:42 am

Hi Stefan,

Thank you for your thoughts. Although it is happening after 5-10 file transfer. so maybe not the file handles, but the memory might be plausible with the scenario as you describe.

But you would not expect this to slow down that much, 50kByte/second is really, really slow.

I think indeed the handling of a file upfront is what is causing it, which is neglectable with large files compared to the time it takes to transfer/write, but with small files, it suddenly becomes very noticeable.

Pieter
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Re: 1000+ file transfer

Postby WhoCares? » Fri May 21, 2010 9:52 am

Just so that I can try if I find the time: Are all the files to be copied in a single directory or are they spread over several directories? And a ballpark figure about the average size of the files would be nice, too. And last but not least: How do you transfer the files?

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Re: 1000+ file transfer

Postby sjpete » Sun May 23, 2010 9:16 pm

Stefan, Whocares,

I did do a few more tests. Limited to only copy to one directory, On the source (XP machine), generated 512 small testfiles of 1.09kByte in one directory and another directory with 256 files of 670kByte (just copy/paste of all the first file, two files, four files etc.)
Copying this time with drag/drop in two windows explorer windows, to a new directory on the NAS.
Some observations:
Copying 50 or so files is quick, until the directory already has a bunch of files in there. The copying itself delays, and than either goes quite quick, or starts that intermittent behavior: copy a few files, pause, and copy again a few files. I could not figure out when that happens.

So maybe it is not the amount/size of the files to copy, but what is already there??? Maybe in the subdirectories as well? (both gets large during copy large number of files/directories).

What might support that, if few 100 files are at the NAS directory, and with Ctrr-A (select all) and delete, it takes quite a while before the 'Delete confirm comes up.
Also copying the same files with overwrite slows down the NAS down even more.

This scenario is easy to create and reproduce.

Thanks, Pete
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Re: 1000+ file transfer

Postby sjpete » Tue May 25, 2010 8:17 pm

I tried FTP, no problem there. It is copying the files pretty fast, considering the overhead for each file with FTP. So I'll try that for a few days, or RMA the unit.
Pete
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Re: 1000+ file transfer

Postby hackmaster » Tue Jun 08, 2010 8:32 pm

I know this post is older, but try TeraCopy. It has some more diagnostic information and will let you know exactly what is going on with the transfer.

Just google TeraCopy, it will direct you!
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Re: 1000+ file transfer

Postby sjpete » Tue Jun 08, 2010 11:13 pm

Hi Hackmaster,

Thanks for the suggestion.
I have Teracopy (nice with the slower Directory Opus copy), just updated from 2.0 to 2.12. It shows the same slow behavior. The prefetching of Teracopy goes fast, it's getting the data over to the NAS/NAS latency. Its starts pretty fast, but starts to crawl after a few seconds (a file per second or so).

For files of few Mb (e.g. mp3) there are no issues using the standard windows copy/move.
FTP seems to be the fastest way for small files.

My guess it is the overhead on the NAS to handle files (file admin etc). When handling is done while transferring, and the file is done before the file handling is done, the next file will wait for that.
With larger files, this is not an issue, as the handler is done before the file transfer itself finishes. My 2 cents...

Pete
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