Speed NAS542

brolysan Posts: 2  Freshman Member
edited July 2020 in Personal Cloud Storage

I have a Zyxel 542 NAS containing 4 HDs of 1 TB each. I want to replace them with HD of 4TB and therefore, I copy all the data from each hard drive to my PC. I have a 1 Gbs network. Data copying is very, very long. I NEVER NEVER exceed 20 MB / s. Is this normal?
1 TB HD is 7200 rpm.
It will take me whole days to simply copy 3 TB of various data.

It s a joke?



  • Mijzelf
    Mijzelf Posts: 2,645  Guru Member
    First Anniversary 10 Comments Friend Collector First Answer
    My French is not what it should be, but I think I read 'Moving 218990 files from NAS to PC'. If that is true, then there is your problem. A harddisk has a typical random access time of 20msec. Which means that putting the disk head above the start of that files alone takes 4380 seconds, when their position is already known. Add the time needed to find&read filesystem structures to know that location, and this can be easily doubled. Then we are talking about 3 hours of only moving heads.
    Depending on the size of the files (which cannot exceed 4.5MB on average), this can easily be more than the actual transfer time. On a gigabit network you can transfer at around 100MB/sec. When on average each file takes two head movements, than that takes 40msec. In 40msec 4MB could have been transferred, so when transferring 4MB files the throughput cannot exceed 50MB/sec. And it gets worse when the files are smaller.

    You should get a higher total throughput when you transfer from more volumes simultaneously. In that case one disk can stream, while the other is seeking, and the cache on the NAS fills the holes.
    Unless you are streaming /to/ a single conventional disk, in which case all math applies to the target too.

    BTW, if your are really 'moving' the files, the throughput is worse, as after reading the file the disk cannot advance to the next one, it has first to move it's head to the directory entry to erase the file, costing at least another 20 msec. If you are planning to dispose the disk, or put another filesystem on it, you'd better copy.
  • brolysan
    brolysan Posts: 2  Freshman Member
    and my english is also average ... lol
    actually I made a cut / paste. I will see then to simply copy / paste. It is about archives therefore a lot of images, psd, ind and others. Some uncompressed videos too, but hey, I still find it slow.

    Thank you very much already for this answer anyway.

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