MSA 2060 with 18 x 3,8TB SSD

[leo-ehk]

Dear Jon from HPE

thanks for you very good support, i also will using the MSA-DP+ on our new MSA Storage. 

We have 18 x SSD drives and im thinking about to running 18 x SSDs with  MSA DP+ on 1 Pool. (Only Drive 1)

Or 12 drives MSA DP  Pool A + and 6 drives RAID 6 on Pool B.

Could you give me a recommendation for this setup ?

Thanks in advanced!

[support_s]

System recommended content:

1. HPE MSA 2060 Storage Array - Specifications

2. HPE MSA 2060 Storage Array - Overview

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[JonPaul]

@leo-ehk 
With having all SSDs the performance of both controllers can be maximized.  So if you are looking for maximum performance then using 2 Pools would be better.  If on the other hand you are looking for more capacity then using a single pool would be better, you will lose 20% + 2 drives of capacity with MSA-DP+ (20% to RAID 6 and 2 drives for the spare capacity).  If you do the additional RAID 6 you will lose 2 more drives to parity (33%).
You also should look at how you will be using the drives,  would all the volumes in the same pool be easier to manage rather than aggregating LUNs on the host side to meet capacity needs.
And remember you will not be able to expand the RAID 6 on the second pool,  Pool expansion on the second pool would be by adding another disk-group.

You could start with the 12 drive MSA-DP+ and see if the performance meets/exceeds your needs.  If so then add the additional 6 drives.  If not then create the second pool and split the workload.

[support_s]

Hello,

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[leo-ehk]

Hello JonPaul,

thank you very much for your answer.
I m sure that the performance with one pool meets our needs but is the config also secure with the fault tolerance.

Is it OK if we connect 18 SSDs in one group and pool? With 18 SSDs I see a bigger problem if 2 hard drives fail than with 6 or 12 SSDs.

Or can more than 2 hard drives fail with 18 SSDs?

Many thanks in advance!

[JonPaul · Accepted solution]

@leo-ehk 
Here's some extra reading about MSA-DP+ disk-group:  https://www.hpe.com/psnow/doc/a00103247enw

MSA-DP+ disk groups can withstand 2 simultaneous drive losses,  same as RAID 6.  It also has built in spare caapcity which is distributed over all the disks so when a drive faults the rebuild starts immediately and will rebuild to many drives. As opposed to RAID 6 where all reconstructed data needs to be put on 1 drive, and therefore limited to the transfer speed of 1 drive.  The rebuilds take less time as each drive has a small chunk to rebuild and you get the aggregated transfer speed of all the drives during rebuild.  The more drives in an MSA-DP+ disk-group will lead to more rebuild speed.
After the initial 2 drive losses if the rebuild completes the data is fully RAID 6 fault tolerant so you can lose an additional 2 drives.  If you specify additional spare capacity when you create the disk-group (CLI only option) after another rebuild you can lose another 2 drives.
If you have a lot of drives in an MSA-DP+ disk group you also have the benefit of "luck" similar to RAID 10 where you can lose many drives but only if they are the "right" drives, if you lose both sides of a parity chunk then you lose all the data.  The Stripe Zones in MSA-DP+ only span 10 drives so when you lose 2 drives there will be stripes of data which are FAULT TOLERANT, some which are DEGRADED (one chunk missing) and some will be CRITICAL (two chunks missing) so if you lose another drive as long as it does not contain chunks from a CRITICAL stripe zone your data is safe.
It can be a bit dizzying to understand. 
Short answer:  MSA-DP+ is better than RAID 6 and better the more drives included.  MSA-DP+ allows up to 128 drives in the same disk group.

[leo-ehk]

Hello JonPaul,

okay perfect and many thanks for your very good help.

Many greetings from germany

[Sunitha_Mod]

Hello @leo-ehk,

That's Awesome! 

We are happy to hear yoour concern has been addressed.