Very slow file splitting to USB sticks

[hlloyge]

Hello all!

I've noticed that file splitting to USB stick, which HAS to be formatted for FAT32, is very, very slow. When I use 7-zip without compression, I get write rate of around 200 MB/sec (which is OK for that stick, it's rather expensive one ), but file splitting to 3 GB limit goes around, ah, 20 MB/sec?
Can something be done about it?

[Stefan2]

Yes, split to hard drive and copy the result to USB stick.



 

[hlloyge]

That would be workaround. Why is it so slow while working with USB flash drive? Is there possibility for a fix?

[Dalai]

USB drives usually have their cache disabled. And file splitting writes probably many small fragments, which is slow without a cache.

Regards
Dalai

[ghisler(Author)]

Yes, this happens because I cannot use CopyFileEx to write parts to the stick, I have to use a ReadFile/WriteFile loop. Although I write in multiples of the cluster size, writing is very slow due to the disabled write cache. But you can manually enable it, then it will be much faster. But then you have to unmount the stick via system tray (near the clock) before unplugging.

[hlloyge]

Damn. I've used same function in Linux in Double Commander, and it works as fast as it should... but I guess there is a big difference between the copy methods in those two OSes.
But how come file splitting with 7-zip without compression works at full speed?

[Usher]

But how come file splitting with 7-zip without compression works at full speed?

7-zip uses local HDD for temp files.

[MVV]

ghisler(Author),
Which buffer size does Split function use? Maybe its buffer could be enlarged?

[ghisler(Author)]

Yes, that's a good point. Or maybe try to use file mapping to copy - I think I read somewhere that CopyFileEx uses file mapping.