MSA 2060 capacity planning

[KevinYeung]

Hi all,

I am installing a msa2060 with 1.2T * 18
For raid 6. It “should be” 19.2T. But the system take too much space for “overhead” and outcome 16T only. May I know to achive 19T space ?

Kevin

[KevinYeung]

I also tried to use raid 5 but the system only able to see 16*1.2T harddisk

[JonPaul]

@KevinYeung 
The MSA is limited to using only 16 drives per RAID set with traditional RAID levels (RAID 6, 5). To utilize more drives in a single RAID set you will need to use the MSA-DP+ raid level.  MSA-DP+ is more fully explained in the virtual storage technical reference:  https://www.hpe.com/psnow/doc/a00103247enw

By default when you create an MSA-DP+ disk group there is RAID 6 overhead (2 drives) and also included Spare capacity (2 drives).  So in order to get the 19.2 TB of available capacity you will either need to add 2 more drives (Recommended) or remove all the included spare capacity (not recommended).  The good news is that the MSA-DP+ will allow you to create the disk-group today and then in the future add incremental disks to the disk-group to increase capacity. There are a number of other benefits gained by using the MSA-DP+ which can be seen in the reference guide.

[KevinYeung]

Hi JonPaul,

Thank you for your suggestion. Finally I added 2 more 1.2T HDD and create two disk group. ( 10 HDD each )

I can see 21T from MSA. Attach to windows 2019 only 19.2T left (customer insist to have 19T)

Is there any risk I did this way? Or I have to recreate and use MSA-DP+?
(Surely I will try DP+ next time)

Thanks a lot
Kevin

[JonPaul · Accepted solution]

@KevinYeung 
Did you create both disk-groups in the same pool?
No risk in creating 2x disk-groups but you miss out on all the benefits of MSA-DP+.
  - Single Disk-group
  - Incremental expansion
  - Faster rebuilds
  - Always in Power of 2 - benefit for sequential WRITE performance
  - Built in spare capacity / no idle drives

The configuration you chose is the traditional method using RAID6 with 10 drives follows the Power of 2 recommendation.  This would have been the recommendation prior to MSA-DP+ raid level availability.

[KevinYeung]

Hi JonPaul,

My engineer told me that he tried to selected all 1.2T * 20 with MSA-DP+. The system will takes 1.2T * 6 for “overhead” meaning 16.8T left.

But you are right. Should try to use DP+ and enjoy those benefits. Will remind the team to plan this way going forward.

Kevin

[DataCenterOperator]

you can reduce the overhead alias spare capacity to 1 or 0 disk space if needed. but for sure is has negative impact for redundancy.

[JonPaul]

@DataCenterOperator 
Reducing the Target/Actual spare capacity if not recommended for HDDs (see Best Practices for HDD and SSD best practices)
Reducing to 0 spare capacity will only be slightly better, in terms of fault tolerance, than a RAID 6 with the number of drives you have allocated.  
Also note that changing the Target Spare Capacity to less is an immediate change,  to return that capacity to Actual Spare requires adding additional disks,  so reducing the Target Spare is not recommended.