topic Re: Nimble Parity reconstruction in HPE Nimble Storage Solution Specialists

Nimble Parity reconstruction

SEENIVASANP — Wed, 18 Nov 2020 13:17:13 GMT

Hi Team,

As all we know nimble uses Triple HF series and Triple+ for AF parity.

Can you help me to understand how parity reconstruction will be happen when it's single drive failure, dual drive failure, 3 drive failure?

Re: Nimble Parity reconstruction

Candhade — Thu, 19 Nov 2020 09:07:25 GMT

AF-Series Arrays have Spare chunks on every SSD. If we have 24 SSDs in the Array,

1st RAID set will be (20+3) meaning 1st chunk on 24th SSD is not taken as it is marked as Spare chunk.

2nd RAID set will be (20+3) meaning 2nd chunk on 23rd SSD is not taken as it is marked as Spare chunk.

So it goes in this fashion. When a drive fails, spare chunk works much the same way as a spare drive does.

The data and parity within failed drive are recalculated using remaining data and parity blocks and then stored in the spare chunk. This is performed by working through every stripe with valid data, rebuild missing data and write the data to the appropriate spare chunk.

Same process will be applied even if there are 3 simulateneous drive failures. If 4th drive also fails before the rebuilding completes, Intra spare (which exists inside every chunk) will be used to reconstruct that data.

In HF-Series, there is NO Spare drive or Spare chunk. So if a drive fails and once the drive is replaced, data is reconstructed and written to the replaced drive. If 3 drives in a HF-series fail before any of the failed drive is replaced, Array will automatically shutdown to prevent failure of any more drives which is a configurable option.

Rebuild to Replacement (Physical) Drives in AF-Series

Walk through each stripe with valid data

Copy data/parity from spare chunks back to replacement drive if available, OR

Rebuild data/parity from the rest of the drives and write to replacement drive

After rebuild process is complete, every spare chunk is erased and returned to the drive as “overprovision” capacity

Re: Nimble Parity reconstruction

SEENIVASANP — Thu, 19 Nov 2020 13:27:52 GMT

How many raid set maximum created with 24 HDD's in AF array (20+3) and 1 Spare HDD?

Re: Nimble Parity reconstruction

SEENIVASANP — Wed, 25 Nov 2020 10:29:39 GMT

Any help on the below one?

Re: Nimble Parity reconstruction

Nick_Dyer — Wed, 25 Nov 2020 10:33:26 GMT

It's a single Triple+ Parity RAID with 21x HDDs in a hybrid flash array.

Re: Nimble Parity reconstruction

Gangasuthan — Wed, 15 Mar 2023 01:03:45 GMT

I have a question on rebuild time when fail drive is replaced. Do we have any information on that? Particulary on Alletra 5010 model.

Re: Nimble Parity reconstruction

Sunitha_Mod — Thu, 16 Mar 2023 10:52:11 GMT

Hello @Gangasuthan,

Thank you for writing to us!

Since you have posted in an old topic and there is no response yet, I would recommend you create a new topic using the create "New Discussion" button, so the experts can check and guide you further.