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About pre-allocation of files...


h017ah

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I'm sorry if this is posted in the wrong forum or if it's answered some other place, but here we go...

How do I make µTorrent allocate all the files when I start the torrent?

Turn on "Pre-allocate disk space" in Torrent Options. Turning on this option will prevent compact storage and sparse files from working, however. All files will be allocated regardless of if you used selective downloading. This is not planned to change in the future. There is little use to pre-allocate except for making sure you have enough space when starting a torrent. It does NOT reduce fragmentation as compared to not using it, since µTorrent allocates the full file when writing without pre-allocate (unless you use compact storage or sparse files).

Doesn't pre-allocation work like it should in for instance Azureus? As I understand, the sole purpose of pre-allocation is to avoid fragmentation and to make sure you've got enough space available, and after my understanding this works well in other BitTorrent clients... why doesn't it prevent fragmentation with µTorrent?

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It doesn't prevent fragmentation any more than NOT using it would. Why? µTorrent allocates the full file whenever it writes a piece to it. Even if you were downloading many torrents, every file would get their own block of space allocated at full whenever they were created, so they'd be as contiguous as the free space. Pre-allocate just does it for ALL files at the beginning, but in reality it doesn't make any difference.

The exception is if you use compact storage or sparse files (which you can't use on pre-allocate)

Like I said there, the only practical use it has is to make sure you have enough space for the entire torrent. (Why it's really needed I don't know, it's not like every tracker doesn't already show you the size of the torrent before downloading, and you would probably know how much space you had left if you were low...)

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well.. as long as you guys can guarantee that this form for allocation prevents fragmentation, it's good for me... what exactly, if any, is the difference between Azureus's way of pre-allocating and µTorrent's way of doing it? The reason I'm asking is because I know that Azureus physically writes the files with zeroes before starting the download.. And I can't see that µTorrent is doing the same...

It's my impression that µTorrent's pre-allocation only reserves space, but doesn't actually write it, so the files can be fragmented during download anyway... and that ain't good..

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What i REALLY need is, "WRITE ZEROS TO FILE" when preallocating the space for the file!

All my torrents are on a network drive on another computer, so the only way to prevent fragmentation is writing the complete file BEVOR you actually start downloading it.

The current "pre"-allocation actually does nothing for me :(

But THX for all the good work!! Keep it going :)

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pre allocating space will create the files and write zeros to them. if its disabled then all that will happen is the files will be created in the mft but no data will be written to them until any is receieved. i have had no fragmentation at all on any of my torrents when using pre allocate disk space.

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