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I am confused by the usable capacity i am getting from a PS6510 with 48 x 2TB Disks. So total this Array has 96TB RAW but after the initial configuration I manage to connect to the array and apply a RAID 6 configuration. The GUI notes that the usable capacity should be 69.08TB with 47 disk in use and one spare. After applying the config the arrays usable capacity immediately jumps up to 26.64TB and has stayed there for the past 5 hours. There are no errors on the array but the RAID Status is "verifying" and progress is at 6%.

I have looked all over and cannot find any documentation on this behavior, and it is pretty concerning for a storage device to give you only 28% usable capacity even with any RAID configuration.

Is this normal? Does it just need to complete verification of the RAID before it will give access to the whole 69.08TB capacity? And if so why would it give access to 26.64TB before verification has completed?

UPDATE: after completing the verification the PS6510 remained at 26TB of usable storage. I then safely rebooted the device and it defaulted the other Type 10 controller. When viewing the disks on this controller it had more then half marked as foreign disks instead of online. From there i managed to readd those disks and the available space jumped from 26 to about 53TB still 16TB shy of the orginal configuration estimate of 69TB. at this point I have absolutely no idea why it is creating a 53TB storage pool instead of a 69TB storage pool.....

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    I want to make sure I'm understanding this correctly. You're creating a single RAID-6 across 48 members? If so, that is not going to work well at all. – Spooler Jul 19 '17 at 20:49
  • wow i wish i had 48 PS6510 a couple PB of storage would be super cool. But no it is a single PS6510 which has 47 disk in a RAID6 and one spare drive. – Zygodactyl Jul 19 '17 at 21:29
  • also you are correct about creating a RAID across mutiple members. As far as I know for the PS series only one RAID can be configured per member. – Zygodactyl Jul 19 '17 at 21:33
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    No, a single PS6510 with 48 disks and a single RAID-6 abstraction with all those disks joined. Right? RAID-6 doesn't handle more than about eight disks tops well (not only will you get diminishing performance returns, your performance will decline with every new disk you add beyond a certain fairly low point), and the chances of more than two disks failing before replacing / re-balancing can occur is pretty high in such a configuration. – Spooler Jul 19 '17 at 21:33
  • Weird, Dell recommends you use a RAID 50, 10, or 6 in there documentation. That being said this PS6510 is only being used as a backup target so speed is not a concern but rather redundancy balanced with capacity. – Zygodactyl Jul 19 '17 at 21:35
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Ended up fixing this by completely factory resetting the device. Then doing the initial config and letting the device sit around for around an hour before picking a RAID Configuration for the Array. As far as I can tell, the secondary controller takes a while to initialize Which somehow causes the RAID configuration to not properly be set on that controller. Hence the weird 26TB of space. Then once the array restarted it defaulted to the other controller which saw over half of the disk as foreign. You can add these disks to the array on that controller but since the other controller already has those disk marked as active it does not increase the usable capacity. Note that an older firmware (5.0.4) was on this device but it was out of warranty so I could not get the new firmware package. That being said this is all just conjecture, but at this point the Array has been humming along for over a week without issue.

TLDR: this was caused by a weird firmware bug. Either update the firmware and factory reset the device or factory reset the device, do the initial config, wait an hour, then apply the RAID config to the array.

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