What does preallocating help reduce fragments when downloading torrents

The Steam BETA has stopped preallocating disk space and just downloads the games "the normal way" April, Seems not so: it definitely preallocates space prior to patching. Last edited by TorMazila ; 12 Apr, am. Showing 1 - 15 of comments. The point of 'allocating space' is to make empty files that will be filled with data as it is installed.

This is to make absolutely sure that not only is there enough room before the installation starts, but that nothing that happens during the installation can suddenly take space that the installer thought it was going to have access too. Washell View Profile View Posts. With a niche setup come niche problems. You fix them yourself or you live with them.

It's unreasonable to expect a company to accommodate you. In a regular setup the pros of doing this outweigh the cons, as JPMcMillen explained.

Last edited by Washell ; 22 Aug, pm. So yes there is a valid reason to disable pre allocate. Originally posted by JPMcMillen :. Several functions may not work. Please re-enable javascript to access full functionality.

Posted 19 May - PM. So the Program in question is Deluge and it has two options for file allocation: Full Allocation or Compact Allocation and I'd like to know which is best for my torrents not Fragmenting my drive.

The problem is, my drive is a 4TB and 2. Defragging it does nothing. I read somewhere on the internet that Full Allocation prevents defragmentation but I'm not sure if that's the file itself or the empty space. I tried posting in the Deluge forums but their Registration has a question that states "What answer to the above question is named after a person?

Already on GitHub? Sign in to your account. It easily maxes out my 1Gbps down fiber connection. The problem qBittorrent is having is it's bad seeding performance. I have done a little experiment to double-check weather I'm wrong or not.

I have a Mbps upload connection and tried seeding a torrent being the only seeder. My friend then tried to download the same torrent at his house just down the road using the same internet provider.

He has a 1Gbps down connection as well and a decent PC running a x just like mine, keeping in mind we're both using M. He started downloading the torrent and successfully connected to me just like it was meant to but the speed I was seeding at was SO LOW. I do not have any speed limits set up at all. I then tried sending him the same file through FileZilla and instantly maxed out my upload speed so I'm more than sure that this is not a connection or a hardware related problem.

I would love to see this problem being fixed as qBittorrent is a truly amazing and nearly perfect piece of software which I always use. The text was updated successfully, but these errors were encountered:.

This bug is now fixed in libtorrent and version 4. Did you use the embedded tracker when sharing the torrent with your friend, or was this a public torrent for which you happened to be the only seeder? Make sure to redact any potentially sensitive data in these files before posting.

Sorry, something went wrong. The torrent was a public torrent and yes I was the only seeder. ACFiber try to set your cache manually to some high value then, like I suggested above. ACFiber 4. So even if the source peer could read and deliver contents at much higher speed without problem, it is in fact the downloading client that CANNOT request more data from the source because that client is already too much busy, waiting for the completion of very large volumes of unnecessary writes.

Even if files are downloaded sequentially, writing them progressively to the filesystem with progressive growth of the filesize causes also unnecessary stress to the filesystem due to many successive allocation for extra space. You'll observe then that very large files e.

Once this is "initialization" with null sectors is done in the client, the download will restart at normal speed if there are sources still connected, otherwise the client will have to find new sources : it is clearly not a limitation of bandwidth the network or from sources, but purely a local limitation of how downloaded files are written to disk with excessive use of the disk bandwidth and excessive flushing of the filesystem cache by these large amount of written bytes, even if these bytes are all zeroes!

It makes NO sense at all to NOT preallocate these files whatever their actual filesize , just to see a bit later that the files cannot fit the remaining free space because qBittorrent has attempted to write a file fragment too far away from the start, this should be done early even before trying to download the first fragment from any position in file!

One way to solve it would be to first start allocating the whole filesize on disk, but NOT by using file writes with null bytes which is very slow, notably on RAID arrays, whiuch instantly will experiment a huge spike of activity , but by using the filesystem call to preallocate the file size the filesystem will allocate enough clusters on disk, but will track that these clusters are still not filled with significant data, so reading from them will just return a buffer filled with zeroes, without even having to read them from disk, so this also saves a lot in the filesystem cache.

The same remark can apply to any other torrent downloader on any OS and filesystem: as much as possible, you should preallocate the storage space, using the best API for each OS that does not require using filewrites with buffers filled with zeroes: such API also exists in Linux! All you have to do normally is to use a "lseek " call or similar, with some flag indicating that it must go "past the current end of file" instead of returning an error the OS may return an error if this cannot be satisfied because of lack of available free space on the filesystem, or because of exhaustion of the write quota allowed for the current user or process ; then you wan write to the file from that position the file must just have been opened with a "random access mode", and not just a "sequential access mode".

The torrent would be added very quickly to qBittorrent, and everything would keep running just fine. But then the moment that new torrent started receiving data, qBittorrent would freeze with high disk activity. Even on a fast SSD M. Not preallocating these files will stress a lot the SSD, and will accelerate its wearout because these sectors will be actually written twice: the first time with massive fills with zeroes, unless the SSD hardware or the filesystem in the OS handles specially theses sectors that are intended to be all-zeroes, the second time with the actual downloaded data.

Yes, we need preallocation of downloaded files and this MUST be the default for downloading any file that is larger than about 4 megabytes, or if downloads are not performed sequentially, or not performed in random order but limited to a maximum "sliding window" of 4 megabytes. If your system supports "sparse files" APFS, NTFS, some Linux filesystems this hould be used as much as possible, but if you don't, and you just use normal filewrites with buffers filled with zeroes, you won't gain anything.

Preallocating files with the correct API will make use of the "sparce files" support in the filesytem, it will be very fast even on rotating hard disks and RAID arrays , will preserve the performance and efficiency of the filesystem caches and other competing processes on the system , will preserve the lifetime of your physical volumes, and will allow much faster downloads of torrents, even in random order from any starting position.

But the random order should still use a "sliding window" whose size should not exceed a few megabytes. DO NOT move the slowing window before you've downloaded and written all bytes at start or end of the sliding window, but continue downloading from remaining "holes" in that window.

You may want to extend this window size only if all space in the "sliding window" is already ordered to connected peer sources and all these sources have a non-zero download rate averaged on the last minute , but you have new candidate sources, but be conservative in how you extend this size and do not allow new peers to extend from any random position in the file, but only onto file fragments that are the closest to the current sliding window.

Turn on "Pre-allocate disk space" in Torrents. Turning on this option will prevent compact storage and sparse files from working, however. Pre-allocate no longer allocates all files when skipping files, only the ones you choose. Firon Posted February 24, Posted February 26, Firon Posted February 26, If you require different behavior, that is what diskio.

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