NFS or Windows Share transfer slows down after a few GBs in NAS 540

Juca Posts: 2  Freshman Member
edited September 2018 in Personal Cloud Storage

I have issues with my NAS 540. I have it configured as RAID 10 (4 x 5TB HDs, approx. 10TB Logical drive).

As I backup some large files (10GB - 250GB) I notice that the transference starts fast enough (120MB/s) but after 2 to 3 GBs the transference slows to about 45MB/s all the way until the end. This is quite disappointing as it takes more than twice the time to transfer the files than expected.

I don't see any tuning options. Please help!


  • Mijzelf
    Mijzelf Posts: 2,645  Guru Member
    First Anniversary 10 Comments Friend Collector First Answer
    120MB/sec is about the max a gigabit connection can handle. If the disks can handle only 45MB/sec, then it will indeed slow down after 1.5GB. The internal memory is 1GB, which will fill up at 75MB/sec, which will take 12 seconds. In this time you have transferred 1.44GB.

    Apparently the network isn't the problem.  The disks should be able to do more, I think, although I don't have experience with raid10. You can login over ssh, and run top while transferring, to see if some process is eating CPU cycles, slowing down the transfer.
  • Juca
    Juca Posts: 2  Freshman Member
    Hello Mijzelf. Your observations make a lot of sense. Since the NAS could be struggling with the RAID 10 array, I decided to factory reset the NAS, remove the drives from the array, and test them as JBOD. I only tested two drives, one at a time, to discard any HW issues, but the poor performance continues:
    • HDs are HGST Deskstar NAS. The write benchmark for them is 146Mbs per second
    • Tested both CIFS and NFS transfers. Performance is very similar with both, but the load on the NAS is higher on NFS. I don't see anything obvious eating up CPU cycles on the NAS
    • I'm copying a 14Gb file from an idle Server. I tested the same file between two servers using NFS, and I get 90MB/sec
    • Memory on the NAS was always under 15%, so I don't see that the NAS is running out of it.
    • Like I mentioned before, the transfer starts very high, around 120MB/sec, then starts slowing down to almost zero, then it goes back up to another 120MB/sec, and slows down. The NAS just continues the cycle, maybe 10 times before it finishes with the 14Gb transfer

    This was my test with NFS:

      rsync -aP /backup/dump/vzdump-qemu-212-2018_08_23-20_15_03.vma.lzo /mnt/nas540/

      sending incremental file list


      14,286,230,731 100%   53.02MB/s    0:04:16 (xfr#1, to-chk=0/1)

    Here's the test again with CIFS/SMB:

      rsync -aP /backup/dump/vzdump-qemu-212-2018_08_23-20_15_03.vma.lzo /mnt/nas5402/

      sending incremental file list


       14,286,230,731 100%   53.92MB/s    0:04:12 (xfr#1, to-chk=0/1)

    Zyxel team: any comments??

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