Extremely Slow Disk Space Pre-Allocation.

[54m4d]

Please provide the following information

qBittorrent version and Operating System

Release-4.3.3 (64-bit)

If on linux, libtorrent-rasterbar and Qt version

N/A

What is the problem

• Very slow disk space pre-allocation.

• This usually happens for quite large size torrents.

• For small size torrents, this usually is not a problem, but if many small torrents are added at the same time, the problem arises.

• It will take hours and hours for the pre-allocation job to slowly finish up. (depending on the size the torrent(s)).

• Pre-allocation is much faster when tested using other clients.

• When pre-allocation option is turned off, the problem does not exist and there is no slowness.

• This issue makes the OS slow and lagging too.

• Makes currently downloading torrents stop or go down to 0 B/s. (see screenshot).

What is the expected behavior

-The expected behavior is a faster pre-allocation.

Steps to reproduce

-Add many small torrent files at the same time or a big single torrent file and let it pre-allocate. Pre-allocate disk space for all files (must be enabled)

Extra info(if any)

• Running Windows 10 64-bit. (10.0.1xxxx)

• Currently having 14 torrent files ranging between 14 and 125 GiB. per file.

• Not using the drive where the OS is installed.

Screenshots

So why is disk space pre-allocation extremely slow?

[The5kull]

Your are using an USB drive which can't keep up with qB. Average response time of 7361 ms is high so qB is waiting for the disk to finish his jobs.

[eurobank]

Same issue happens WITH other clients and it is normal, especially with slow drives and large files.

[FranciscoPombal]

Makes currently downloading torrents stop or go down to 0 B/s. (see screenshot).

This is expected if you're preallocating in the same drive.

About preallocation being "slow": that depends entirely on the specs of the drive. Off-the-shelf USB drives tend to be slower. Also, USB 1.0-2.0 is half-duplex, so that is another massive hit to performance if you're not using USB 3.x or higher.

[jbruchon]

I have had this issue forever. Preallocations need to be serialized per-device. I have drives capable of writing near 180 MB/sec that will have two torrents allocate simultaneously, then Resource Monitor shows both preallocating at 2 MB/sec. Only one preallocate should be issued at a time.