3 Replies Latest reply on Jul 28, 2013 11:14 AM by Merwinsson

    6TB to 8TB array expansion took 3.5 DAYs - is this expected?

    Merwinsson

      I added another 2TB disk to my array on THU in the wee hours of the morning and the array migration just finished, 3 1/2 days later.

       

      So far, things look good, but 3 1/2 days!?

       

      I know a 8TB RAID5 is pretty big, but still, I expected something more like several hours.

       

      My CPU is not a powerhouse, it's only a Celeron 430 1.8 GHz because this machine does nothing other than host storage, but still, the CPU has nothing else to do...and there is 2 GB of RAM.

       

      The migration runs in the background and the array can still be used , and that is a nice thing, but what about users who just want to get the job done as fast as possible.  Is there some way to speed up the migration.  I was thinking along the lines of a registry setting or increasing a process's priority.

       

      Does anyone else have an experience in array capacity expansion to share?

        • 1. Re: 6TB to 8TB array expansion took 3.5 DAYs - is this expected?
          kevin_intel

          Hello Merwinsson,

           

          Based on the hardware description you provided, the time that took this array expansion is completely normal.

           

          This is because, the system working with 2 GB of RAM memory is just the minimum RAM for the system. The processor Celeron 430 is a good processor but not that powerful to complete the action faster. Besides these two reasons, I would say that the capacity of the new Hard Disk Drive is too big and it also takes time to complete the process based on the HDD capacity.

          • 2. Re: 6TB to 8TB array expansion took 3.5 DAYs - is this expected?
            Merwinsson

            Is there a publication that gives guidance on how fast the RAID 5 can work based on system RAM and CPU type?

            And when I say "work" I mean a few things, like:

            1) What to expect for write performance.

            2) What to expect for initialization time.

            3) What to expect for verify time.

            4) What to expect for expansion-migration time.

             

            What about speeding up the migration process?

            Is there any way to give it more priority?

            • 3. Re: 6TB to 8TB array expansion took 3.5 DAYs - is this expected?
              Merwinsson

              Might I also ask for an explanation why another expansion-migration I just did took nearly the same time, with the exact same disk models and capacities, yet was done on significantly more powerful hardware?  That would seem to indicate that RST is fairly slow at this type of task no matter what CPU/RAM is at its disposal.  Let me summarize my findings.

              System #1 - Time to expand and migrate RAID5 from 6TB to 8TB = 82 hours (3 days 10 hours)
              Foxconn Q45 chipset motherboard
              Intel Celeron 430 CPU (Single Core, 1.8 GHz)
              2 GB DDR2-800 RAM
              4 Seagate 2 TB hard drives + 1 Western Digital 2 TB hard drive
              Windows 7 Pro 64 bit

              System #2 - Time to expand and migrate RAID5 from 6TB to 8TB = 78 hours (3 days 6 hours)

              Foxconn Q45 chipset motherboard
              Intel Celeron E3300 CPU (Dual Core, 2.5 GHz)
              4 GB DDR2-800 RAM
              4 Seagate 2 TB hard drives + 1 Western Digital 2 TB hard drive
              Windows 2008 R2 Datacenter 64 bit

              Both systems are a vanilla install with no extra software (they are just file servers).

              The 2nd system has twice as much RAM, twice as many computing cores, and each core is over 50% faster than the 1st system.

              So why did it not complete much faster?

              And here is something very bizarre I just discovered.
              According to the event log, system 1 actually completed the migration in 2 days 18 hours.
              I got the original figure of 3 days 10 hours by visually recording the start time of the migration and the time when the RST UI went to 100% and then doing some subtraction.  I personally watched the UI go from 99% to 100% just before my original post at about 2PM on SUN 7/21, yet, the event log lists the migration as being complete at 9 PM on SAT 7/20.  I have no way to explain this, but if you use this new time, that means that system 1 finished significantly faster than system 2 despite being less powerful.  I was only able to use the event log to compute the time for system 2 because I was not present when the UI hit 100%, so maybe the time is suspect, I don't know.  What I DO know, is that using the event log ONLY for the times, a less powerful system migrated faster than a more powerful system.  Strange.