NAS 540 Copy Speed to fill the NAS

NOP1050

I am currently setting up my NAS and need to refill it.
Now I thought the quickest way is to use the copy function with the copy button.
So I connected the USB 3.0 hard drive at the front and pressed the copy button.
But 1.72 TB in more than 9 hours is really slow.
Which way is faster?

Mijzelf

1.72TB in 9 hours a around 50MB/sec. When you have a lot of small files that's not bad.

NOP1050

When I copy from one USB 3.0 hard drive to another USB 3.0 hard drive I get about 170 MB/s.
The hard drive is connected via USB 3.0 to the Copy USB 3.0 socket on the NAS 540, so I expected more!

Mijzelf

170MB/sec? I suppose that is from SSD to SSD? A rotating harddisk (which is in your NAS, I suppose) behaves different. While it can do around 150MB/sec sustained read/write speed, it's the random access time which is killing. To access a random sector, the head has to be positioned, and then you have to wait until the sector rotates under the head. This costs typically 10msec. When you write a small file, you'll have to create a directory entry, which is 1 'random' sector, then write a file node, another sector, and finally write the file itself. A 3rd random access. Which makes 30msec. Let's say the file is 1MB, @100MB/sec that costs another 10msec. So you have spent 40msec to write an 1MB file, which is 25MB/sec. And then I'm assuming the whole target filesystem is cached in memory, so you never have to read something. (Which also starts with 10msec seek time). Smaller files are even worse. A 1 byte file still takes 30msec. Which is around 30 bytes/sec.

Fortunately the random access time of an SSD is not measured in msec, but in microsec. So an SSD can write thousands of small files a second, where a rotating disk maxes out at around 30 files/sec.