Help : Skip Re-checks

[bhamism]

I am downloading 10GB+ files onto a removable drive connected via USB1.1 (yeah, that stuffs ancient.. but thats another story). My utorrent crashed and now everytime i start utorrent it goes into a Checking mode on all the files ... and you know how painful reading and re-checking all the files on USB1.1 can be. Is there a way I can skip the checking again mode and start the download where it left off ??

[DreadWingKnight]

No.

And you don't really want it to anyway since non-graceful shutdowns of software can cause corruption in the files.

[bhamism]

Aah that sucks. now I have to wait an entire day just to get all of the torrents re-checked. No way at all ?

[Falcon4]

It would certainly be nice if there were an option for uTorrent to "pessimistically" reduce the percentage to the last known good write, then continue downloading where it left off... I have several slow computers that take eternities to hash-check and when they crash while DLing, it's a bitch to get back. But... then again... it seems none of our suggestions are taken seriously anyway... *rolls eyes*

[Firon]

It has no real, intelligent way to know what data was written properly to disk and what wasn't.

[Falcon4]

In which case it can drop back to the last time the resume file was written - in which case, considering the resume file was written (and hence read back), the data for the torrents would have been written up to that point as well. Or am I missing something?

edit: In this case it would essentially be "discarding" a small amount of data since the last resume file write... which IMO is a lot better than having to spend time re-reading all 1.6gb on a 200MHz Pentium-MMX or a USB 1.1 drive... in these cases usually I stop the torrent and delete the data anyway!

[Firon]

The problem is that it has no idea if Windows actually flushed the data to disk. Or if the drive's cache flushed the data to disk. I suppose it is possible for it to assume it's been written after some minutes, but one, your PC shouldn't be crashing, and if it is, FIX IT, and two, that just increases the chance of having bad data.

[Falcon4]

but one, your PC shouldn't be crashing

It wouldn't, if uT didn't run it out of memory...

[Condor]

never use your removable drive for use as save large torrent files location, NOT 1.1 usp speed -_-v

[chetbaker]

i have the problem of rechecking again and again. I have a removable harddisk which I never remove. Do I still have to save large torrents on a nonremovable harddisk. I bought the removable just for the large torrentfiles! The larger torrents do not fit on my nonremovable harddisk. Strange that I never met this problem before and only after 50 percent was downloaded fast without rechecking!

[BoundSyco]

Heres one advantage to windows vista. Transactional Files

http://msdn2.microsoft.com/en-us/library/aa365456.aspx

http://msdn2.microsoft.com/en-us/library/aa366295.aspx

For non windows vista:

http://msdn2.microsoft.com/en-us/library/aa364451.aspx

As for the write-back problems of on disk cache: assume a maximum fail size (max disk cache is what, 16-32 megs now?) and update (use two, dated alternating files) checkpoint files every 16-32 megs, latest checkpoint records last known good write. That way at most you would lose 16 to 32 megs of data. Essentially implementing your own transactions, except in this case you dont have to maintain any roll back information because you just assume it is lost.

[chetbaker]

Thanks,

I have read some of the information from your link:

Windows stores the data in file read and write operations in system-maintained data buffers to optimize disk performance. When an application writes to a file, the system usually buffers the data and writes the data to the disk on a regular basis. An application can force the operating system to write the contents of these data buffers to the disk by using the FlushFileBuffers function. Alternatively, an application can specify that write operations are to bypass the data buffer and write directly to the disk by setting the FILE_FLAG_NO_BUFFERING flag when the file is created or opened using the CreateFile function

still I'don't understand how to change the flushfilebuffers function. I don't understand your suggestion as well I'm afraid. The idea I can grip a little but how to change settings I don't understand.

[BoundSyco]

you dont change the flushfilebuffers function. There are two issues at work here:

1) The op system buffers

2) The Hard disk buffers

FlushFileBuffers solves (1). The second issue is incredibly difficult to solve (aka not really possible with a single file). My suggestion is to implement a rudimentary form of transactions that take place at certain specified intervals.

You dont change any "settings" in particular. You simply use the flushfilebuffers function at specific times. The times are dictated by when you choose to update the completed file write section. The idea is as follows:

Assume you have an 8 MB cache:

You begin to write data to the file, the file pointer moves along. After you have written 8 MB of data you call flushfilebuffers, at this point you can't know if data has actually been written to the disk platters or not (all of the data is potentially in the disk cache). You then write an aditional 8 MB of data and call flushfilebuffers. At this point, you are guaranteed (not really, but for all practical purposes you are) that the first 8 MB have been written. You can then write to a completion file that the first 8 MB have been written. In the event of a power failure, you can then read out of the completion file which was the last chunk of 8 successfully written to the disk, thus you only lose 8 MB of data at most.

Thats the basic idea. If you have more questions please read:

http://developer.postgresql.org/pgdocs/postgres/wal-reliability.html

and

http://blogs.msdn.com/adioltean/archive/2005/12/28/507866.aspx