Dell Dynamic Disk Pool available capacity

Hello llya,

So when using DDP all disk are spinning & being accessed all the time. Also DDP is running a raid6 as well so if you were to use a raid calculator you can see what your space would be based off raid6 settings. Also here is a link to the user’s guide of MDSM & if you look on page 97 it explains some more of the differences between DDP & Disk Groups. http://downloads.dell.com/Manuals/Common/powervault-md3200_Administrator%20Guide_en-us.pdf

Please let us know if you have any other questions.

Thank you for your response, but I'm still have questions.

For example.

I have md 1420 connected to MD3420.

MD1420 has 20 x 1TB disks installed.

If I'm creating disk group with RAID 5 + 1 HDD HS then i will have 18*931= 16.7 TB (2 missed from total capacity)

If I'm creating disk group with RAID 6 + 1 HDD HS then i will have 17*931= 15.8 TB (3 missed from total capacity)

But If I'm creating disk pool for all the disks(Preservation capacity 1 HDD) Total capacity will be 14.3 TB (Usable 13.4 TB)and this looks like i messed at least 4.2 TB ( ~ 4.5HDDs)

If you telling that Disk Pool is like RAID6 the capasity should be around 15.8 TB. Even I set Preservation capacity to 0 I will provide 14.3 TB of usable space

Could you comment this?

I'm VERY curious about this issue as well.

We recently purchased an MD3820i populated with 24 1.8TB NL-SAS 10K drives. This unit is marked to replace a 3220i.

The usable space on each of the 24 disks is 1.63691667.

If I were to configure this enclosure as a single RAID6 disk group, using all 24 disks and retaining a single HS, the usable capacity would be 34.272TB

If I were to configure the enclosure as a single Dynamic Disk Pool, using all 24 disks and accepting the default Preservation Capacity of 3,342.432GB (2 Physical Disks) my usable capacity is only 28.109TB.

That's a 6.163TB difference. Where did it go and how can I get it back and still have a fault tolerance level comparable to RAID6 with a hot spare?

Did you find out or get an answer? I just got an MD3420 to configure for the first time and I just found out the same.. RAID-6 gives med ~34TB while DDP gives me 28TB. Both set to tolerate 1 disk failure (hot spare/reserved space)

Has ANYONE gotten an answer? All I get from support is the same old documentation that explains NOTHING about the missing space, or HOW MANY FAILURES a 24 drive disk pool can tolerate.

We are using a MD3420 by the way with 600G 10K SAS drives.