NSA325 - rebuilding RAID 1 3TB disks (75% full) - gonna take weeks!!

I have a NSA325 v1, with firmware 4.81
I noticed that the RAID was "degraded" a few days ago, and it let me just "repair" it, which I clicked at about 8pm on 25/12/2021

its currently (18:36 26/12/2021 - ie about 23 hours in) on 5.6%.  It is going up, but very slowly, and at this rate it will take about 2 weeks!!!!!

It seems to be saying both disks are OK, but I cant believe this is right!

All Replies

  • Dexter
    Dexter Posts: 108  Ally Member
    The repair process might take lots of time due to the data in your disk.
    You may also check the S.M.A.R.T info on your disk to check if there is any issue on your disk.
  • Smart info:

    To copy all the data across is being done about 1-2 MB/sec (assuming 2TB over 10 days), which is very slow!
    anyway I can speed it up?
  • Mijzelf
    Mijzelf Posts: 1,977  Guru Member
    A 325 should rebuild at 50-75MB/sec. Assuming your both disks are healthy, I think something is accessing the disks, next to the rebuild process. Rotating disks are notoriously bad in multitasking, a normal harddisk these days can deliver something like 150MB/sec sustained, while worst case, when it has to deliver 2 or more streams, it can drop to 25kB/sec.
    So stop all your background tasks which access the disk.

    @Dexter Rebuilding a raid array is unfortunately not dependent on the amount of data in the filesystem. At raid level it is just coping with raw sectors, it doesn't know if the filesystem on top has data stored on that sector. All sectors are copied (or XORred in case of raid5/6), including sectors which are not in use. Only the raw size is important. 
  • mMontana
    mMontana Posts: 585  Guru Member
    edited December 2021
    IMVHO cache could improve a bit the timing.
    Cache as "device/system" RAM and hard drive cache, which can optimize the par/movement write ratio if large enough.
    Also, 150MB sustained for 5.400rpm or 7.200 RPM are a bit too much optimistic. 70-80 might be a more realistic transfer rate, IMVHO, unless high performances drives (not suitable on consumer/home NASes like Zyxel ones).
    Moreover: some NAS firmwares allow to balance performances between rebuild and normal operation.
    Hope the OP has a UPS serving its device...
  • Dexter
    Dexter Posts: 108  Ally Member
    Thanks for the information.I'll take a note.
  • I stopped all processes i could find (php was still using 25% tho - thought it best not to kill that!) - I left it, and left it.  It got up to 16% by this morning!  (after 2.5 days!).  Anyway, I did something else and it exited the repair process!!  it just said "degraded" again!!  Oh no, have to start again!!

    well, I restarted the repair at around 12noon, and 9.5 hours later its not on 76%!   Hopefully it will continue at this new rate of knots!!  :-)

    thanks for your guidance!
  • and it finally finished repairing about 11pm, so just 11 hours!  I wonder why it was so fast the 2nd time?