When transferring large files I get an avg transfer with a pretty good rate of around 50MB/s. Then I tried to transfer a folder that contained around 80K small files (around 1-100KB each) and I'm now getting transfer rates around 200KB/s. Does anyone have any info about why there is such a dramatic loss of write speed?

As you can see in this picture, when it goes fast it is copying a single large file, but when it slows down it copies multiple small files; 300 files 1kb each in 20 secs, should be more like less then 1 second for 300kb. This is only when copying a lot of small files not a lot of large files.

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  • what are you writing to and what OS? I presume it is Windows 8 writing to a USB flash drive, but is it USB2 or USB3 (or USB1!) port and what is the exact make/model of the flash drive? Different ports and different drives have different speed capabilities (even though they may be described as 'USB2' or 'USB3' they are not all equal). But speed of 200K/s writing to a flash drive seems very slow indeed. – gogoud Mar 1 '15 at 7:08
  • @fixer1234 But it's an SSD not an HDD like with most computers these days – Kirill2485 Mar 1 '15 at 8:25
  • @gogoud Even when I copy from partition to partition, I still get the same result, a steady 100MB/s when copying one large file, but slows to 800kb/s when copying 1000000 small 1kb files – Kirill2485 Mar 1 '15 at 8:27
  • I feel sure that copying inside an SSD should be much faster than this. Maybe some antivirus thing going on? – gogoud Mar 1 '15 at 8:37
  • @gogoud No, its completely clean. Also at the beginning of the transfer it sais "Discovered 4,503,424 items" for like 60 seconds as seen in this picture: imgur.com/OpaBcai which I doubt is normal behavior. – Kirill2485 Mar 1 '15 at 8:55

Because transferring even 1 byte file involves reading and writing of several kilobytes of data. The smaller file - the bigger overhead.

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  • I do not understand your answer, what determines this speed, is it the proccessor speed, because even on my roomates PC (with a 700MBPS SDD copies small files at 15kb/s)? – Kirill2485 Mar 1 '15 at 5:15
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    The speed is roughly described by ratio (file_size / overhead_size) * throughput. What exactly determines speed is dependent on particular setup. Also, larger cache can be useful. In any case, it won't be very fast. – ilkhd Mar 1 '15 at 5:21
  • And what type of particular setup would make it faster (The processor speed, the RAM, or the video card, etc)... You still didn't explain the answer – Kirill2485 Mar 1 '15 at 6:52
  • I explained it perfectly: nothing will make it much faster and it is unclear what will make it a little faster. Small file transfers will be slow and it cannot be fixed. – ilkhd Mar 1 '15 at 7:49
  • My Azure hosted Windows Server copies lots of small files from one drive to another almost instantly, why is it fast on there then? – Kirill2485 Mar 1 '15 at 8:12

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