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

Juca

Hello,

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!

#NAS_Sep

Mijzelf

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

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

  vzdump-qemu-212-2018_08_23-20_15_03.vma.lzo

  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

  vzdump-qemu-212-2018_08_23-20_15_03.vma.lzo

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

Zyxel team: any comments??