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    LVM Question

    Scheduled Pinned Locked Moved IT Discussion
    lvmlinux
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    • stacksofplatesS
      stacksofplates
      last edited by

      I just thought of this. Possibly MBR disk size lmitations?

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

        @johnhooks said:

        The only thing I could think of was needing extra space, but why not just increase the size of your disk?

        There are a great many cases when you cannot just increase the size of your disks. It is actually extremely common in the enterprise space that many small LUNs be handed to the system and LVM be expected to bind them into a single storage unit.

        stacksofplatesS 2 Replies Last reply Reply Quote 2
        • stacksofplatesS
          stacksofplates @scottalanmiller
          last edited by

          @scottalanmiller said:

          @johnhooks said:

          The only thing I could think of was needing extra space, but why not just increase the size of your disk?

          There are a great many cases when you cannot just increase the size of your disks. It is actually extremely common in the enterprise space that many small LUNs be handed to the system and LVM be expected to bind them into a single storage unit.

          What's the advantage to doing that over RAID 0 and then making one PV?

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

            @johnhooks said:

            What's the advantage to doing that over RAID 0 and then making one PV?

            Reliability. If one slice fails, RAID 0 would hose the full filesystem. With a span there is a lot less "one blip spells total disaster."

            stacksofplatesS 1 Reply Last reply Reply Quote 1
            • stacksofplatesS
              stacksofplates @scottalanmiller
              last edited by

              @scottalanmiller said:

              @johnhooks said:

              What's the advantage to doing that over RAID 0 and then making one PV?

              Reliability. If one slice fails, RAID 0 would hose the full filesystem. With a span there is a lot less "one blip spells total disaster."

              I didn't realize it was more reliable than RAID 0. Thanks!

              scottalanmillerS 1 Reply Last reply Reply Quote 0
              • stacksofplatesS
                stacksofplates @scottalanmiller
                last edited by

                @scottalanmiller said:

                @johnhooks said:

                The only thing I could think of was needing extra space, but why not just increase the size of your disk?

                There are a great many cases when you cannot just increase the size of your disks. It is actually extremely common in the enterprise space that many small LUNs be handed to the system and LVM be expected to bind them into a single storage unit.

                @scottalanmiller said:

                @johnhooks said:

                The only thing I could think of was needing extra space, but why not just increase the size of your disk?

                There are a great many cases when you cannot just increase the size of your disks. It is actually extremely common in the enterprise space that many small LUNs be handed to the system and LVM be expected to bind them into a single storage unit.

                Plus I guess if you're not in control of the Hypervisor then you'd have to make due with what you're given.

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                • scottalanmillerS
                  scottalanmiller @stacksofplates
                  last edited by

                  @johnhooks said:

                  @scottalanmiller said:

                  @johnhooks said:

                  What's the advantage to doing that over RAID 0 and then making one PV?

                  Reliability. If one slice fails, RAID 0 would hose the full filesystem. With a span there is a lot less "one blip spells total disaster."

                  I didn't realize it was more reliable than RAID 0. Thanks!

                  It's not great, the filesystem tends to be unhappy when parts disappear. But if you have 100 slices and one vanishes, likely only a few files will be impacted rather than everything. Not always, but safer at least.

                  stacksofplatesS 1 Reply Last reply Reply Quote 1
                  • stacksofplatesS
                    stacksofplates @scottalanmiller
                    last edited by

                    @scottalanmiller said:

                    @johnhooks said:

                    @scottalanmiller said:

                    @johnhooks said:

                    What's the advantage to doing that over RAID 0 and then making one PV?

                    Reliability. If one slice fails, RAID 0 would hose the full filesystem. With a span there is a lot less "one blip spells total disaster."

                    I didn't realize it was more reliable than RAID 0. Thanks!

                    It's not great, the filesystem tends to be unhappy when parts disappear. But if you have 100 slices and one vanishes, likely only a few files will be impacted rather than everything. Not always, but safer at least.

                    That's kind of awesome. I didn't realize it was that much more reliable.

                    1 Reply Last reply Reply Quote 0
                    • scottalanmillerS
                      scottalanmiller
                      last edited by

                      Also if one slice is slow and the others are fast, you don't have to wait on the one to put blocks together. So temperamental delays are less impactful.

                      1 Reply Last reply Reply Quote 1
                      • stacksofplatesS
                        stacksofplates
                        last edited by

                        And if you have mismatched sizes you would lose space with RAID 0. And can't grow RAID 0 either.

                        Ha I knew it was a dumb question.

                        scottalanmillerS 1 Reply Last reply Reply Quote 1
                        • scottalanmillerS
                          scottalanmiller @stacksofplates
                          last edited by

                          @johnhooks said:

                          And if you have mismatched sizes you would lose space with RAID 0. And can't grow RAID 0 either.

                          Ha I knew it was a dumb question.

                          Very true as well.

                          1 Reply Last reply Reply Quote 0
                          • travisdh1T
                            travisdh1
                            last edited by

                            I ❤ LVM

                            1 Reply Last reply Reply Quote 2
                            • StrongBadS
                              StrongBad
                              last edited by

                              LVM is awesome, it is a great tool.

                              stacksofplatesS 1 Reply Last reply Reply Quote 2
                              • stacksofplatesS
                                stacksofplates @StrongBad
                                last edited by

                                @StrongBad said:

                                LVM is awesome, it is a great tool.

                                I use it all the time. Snapshots are awesome. I've just never needed to use multiple disks and didn't think of the above scenarios when you would have multiple PVs.

                                1 Reply Last reply Reply Quote 1
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