ML
    • Register
    • Login
    • Search
    • Recent
    • Categories
    • Tags
    • Popular
    • Users
    • Groups

    RAID10 Expansion/Reconstruction

    IT Discussion
    6
    22
    2037
    Loading More Posts
    • Oldest to Newest
    • Newest to Oldest
    • Most Votes
    Reply
    • Reply as topic
    Log in to reply
    This topic has been deleted. Only users with topic management privileges can see it.
    • Obsolesce
      Obsolesce last edited by

      I'm doing a RAID10 expansion on a Hyper-V hypervisor. After a whole day of reconstructing, it's only at 3%. Looking at the lights (barely any activity) and testing read/write speeds (they're speedy), I can tell it's barely working. I was under the impression rebuilds/reconstructions happen at 30% I/O on Dell PERCs. It doesn't seem to be doing even that. Is there a way to turn it up? At this rate, it'll take just over a month... I suppose that's okay, but man... if I don't have to wait that I'd rather not.

      == BACKGROUND INFO ==
      (all drives are enterprise drives)

      It consists of an SSD RAID 6x 800GB (for things like SQL servers and other servers that benefit from high I/O), and also a 500GB partition that serves as an SSD cache for the HDD RAID.

      I bought 4x 960GB SSDs (they are better and cheaper than the 800s already in it). I used those to expand the existing SSD RAID, it went well and took less than a day. I went in the Hypervisor and expanded the volume to use the newly available space, all is well, speedy, happy.

      The HDD RAID10 consists of 4x 8TB for the bulk of VM data. I bought an additional 2x 8TB drives to expand the HDD RAID10. Threw the drives in, selected the new drives and started the RAID10 expansion/reconstruction. The reconstruction is going well, considering...

      I tried disabling the SSD Cache for the HDD RAID for almost a day, and that made no difference, so I re-enabled the Cache. 99% of writes are going to the SSD Cache and not the HDD RAID, about 60% reads are coming from the SSD Cache and not the HDD RAID.

      I guess all I'm looking for is a way to increase the speed in which the RAID reconstruction works? Probably not possible from my searches turning up nothing, but I thought I'd ask here.

      1 Reply Last reply Reply Quote 1
      • JaredBusch
        JaredBusch last edited by

        Honestly I had no idea that the PERC allowed expansion.

        Obsolesce scottalanmiller 2 Replies Last reply Reply Quote 2
        • Obsolesce
          Obsolesce @JaredBusch last edited by Obsolesce

          @jaredbusch said in RAID10 Expansion/Reconstruction:

          Honestly I had no idea that the PERC allowed expansion.

          Yeah, more specifically, on-line expansion. I should have specified that above.

          This is being done through Dell's OMSA.

          scottalanmiller 1 Reply Last reply Reply Quote 0
          • scottalanmiller
            scottalanmiller @JaredBusch last edited by

            @jaredbusch said in RAID10 Expansion/Reconstruction:

            Honestly I had no idea that the PERC allowed expansion.

            Same here.

            dbeato 1 Reply Last reply Reply Quote 0
            • scottalanmiller
              scottalanmiller @Obsolesce last edited by

              @tim_g said in RAID10 Expansion/Reconstruction:

              @jaredbusch said in RAID10 Expansion/Reconstruction:

              Honestly I had no idea that the PERC allowed expansion.

              Yeah, more specifically, on-line expansion. I should have specified that above.

              This is being done through Dell's OMSA.

              Keep in mind that mirrored RAID expansion is not reconstruction. Very different things.

              Only Parity RAID has a reconstruction/expansion mixed operation.

              For mirrored RAID to grow, it has to move ALL data off of the original array, rebuild it, and put it all back. It's an insanely enormous operation and there is little operating space for the system to do that. It's actually a pretty amazing technical feat. I can come up with ways to do it, but they are incredibly intensive and require special hardware support. Doable, but there is a reason it is slow.

              Obsolesce 1 Reply Last reply Reply Quote 2
              • Obsolesce
                Obsolesce @scottalanmiller last edited by Obsolesce

                @scottalanmiller said in RAID10 Expansion/Reconstruction:

                @tim_g said in RAID10 Expansion/Reconstruction:

                @jaredbusch said in RAID10 Expansion/Reconstruction:

                Honestly I had no idea that the PERC allowed expansion.

                Yeah, more specifically, on-line expansion. I should have specified that above.

                This is being done through Dell's OMSA.

                Keep in mind that mirrored RAID expansion is not reconstruction. Very different things.

                Only Parity RAID has a reconstruction/expansion mixed operation.

                For mirrored RAID to grow, it has to move ALL data off of the original array, rebuild it, and put it all back. It's an insanely enormous operation and there is little operating space for the system to do that. It's actually a pretty amazing technical feat. I can come up with ways to do it, but they are incredibly intensive and require special hardware support. Doable, but there is a reason it is slow.

                I see, that makes sense.

                I keep using "reconstruction" because that's the "state" of the virtual disk:

                0_1510159139750_Untitled.jpg

                scottalanmiller 1 Reply Last reply Reply Quote 0
                • scottalanmiller
                  scottalanmiller @Obsolesce last edited by

                  @tim_g said in RAID10 Expansion/Reconstruction:

                  @scottalanmiller said in RAID10 Expansion/Reconstruction:

                  @tim_g said in RAID10 Expansion/Reconstruction:

                  @jaredbusch said in RAID10 Expansion/Reconstruction:

                  Honestly I had no idea that the PERC allowed expansion.

                  Yeah, more specifically, on-line expansion. I should have specified that above.

                  This is being done through Dell's OMSA.

                  Keep in mind that mirrored RAID expansion is not reconstruction. Very different things.

                  Only Parity RAID has a reconstruction/expansion mixed operation.

                  For mirrored RAID to grow, it has to move ALL data off of the original array, rebuild it, and put it all back. It's an insanely enormous operation and there is little operating space for the system to do that. It's actually a pretty amazing technical feat. I can come up with ways to do it, but they are incredibly intensive and require special hardware support. Doable, but there is a reason it is slow.

                  I see, that makes sense.

                  I keep using "reconstruction" because that's the "state" of the virtual disk:

                  0_1510159139750_Untitled.jpg

                  Right, well it IS reconstructing. But the term means something different than it does with RAID 5 or 6. With RAID F reconstruction is literally "we told the array it was broken, that the parity wasn't parity but actual data and told it to restore parity to the new drive." Which is just a fancy way to say "We downgraded this RAID 6 to a RAID 5, added a disk and told it to recover."

                  With RAID 10, it's "we are reconstructing the data from scratch in a way that is totally unlike any RAID operation."

                  So one is a reconstruction of your RAID array, the other is inherent RAID reconstruction.

                  1 Reply Last reply Reply Quote 1
                  • Reid Cooper
                    Reid Cooper last edited by

                    Has the percentage increased?

                    1 Reply Last reply Reply Quote 0
                    • Obsolesce
                      Obsolesce last edited by

                      Still at 3%... does about 3% per day so far.

                      scottalanmiller travisdh1 2 Replies Last reply Reply Quote 0
                      • scottalanmiller
                        scottalanmiller @Obsolesce last edited by

                        @tim_g said in RAID10 Expansion/Reconstruction:

                        Still at 3%... does about 3% per day so far.

                        That feels pretty slow 🙂

                        1 Reply Last reply Reply Quote 0
                        • travisdh1
                          travisdh1 @Obsolesce last edited by

                          @tim_g said in RAID10 Expansion/Reconstruction:

                          Still at 3%... does about 3% per day so far.

                          Ouch. Good luck.

                          1 Reply Last reply Reply Quote 0
                          • dbeato
                            dbeato @scottalanmiller last edited by

                            @scottalanmiller It depends, see below:
                            https://www.dell.com/support/article/us/en/04/sln305744/dell-poweredge--how-to-expand-or-extend-a-virtual-disk-?lang=en

                            1 Reply Last reply Reply Quote 0
                            • dbeato
                              dbeato last edited by

                              https://www.youtube.com/watch?v=rbQFJoMm9Ns

                              1 Reply Last reply Reply Quote 0
                              • Obsolesce
                                Obsolesce last edited by

                                It's at 7% now!

                                scottalanmiller 1 Reply Last reply Reply Quote 0
                                • scottalanmiller
                                  scottalanmiller @Obsolesce last edited by

                                  @tim_g said in RAID10 Expansion/Reconstruction:

                                  It's at 7% now!

                                  Speeding right along.

                                  Obsolesce 1 Reply Last reply Reply Quote 1
                                  • Obsolesce
                                    Obsolesce @scottalanmiller last edited by

                                    @scottalanmiller said in RAID10 Expansion/Reconstruction:

                                    @tim_g said in RAID10 Expansion/Reconstruction:

                                    It's at 7% now!

                                    Speeding right along.

                                    Yeah, it's going nowhere fast!

                                    1 Reply Last reply Reply Quote 0
                                    • Reid Cooper
                                      Reid Cooper last edited by

                                      At least it is moving a little.

                                      1 Reply Last reply Reply Quote 1
                                      • Obsolesce
                                        Obsolesce last edited by

                                        Oh I must not have refreshed the page or something... it says 11% now.

                                        dbeato scottalanmiller 2 Replies Last reply Reply Quote 1
                                        • Obsolesce
                                          Obsolesce last edited by

                                          Either that or something caused a bump in percentage... no idea.

                                          1 Reply Last reply Reply Quote 1
                                          • dbeato
                                            dbeato @Obsolesce last edited by

                                            @tim_g That's much better

                                            1 Reply Last reply Reply Quote 1
                                            • First post
                                              Last post