HP MSA 2050 adding disk question

[adam900331]

Hy!

We have a HP MSA 2050 storage, which has adding disk procedure. There are two disk group:

- 8 SAS disk which is related to A pool

- 6 SSD disk which is related to B pool

There is no spare disk.

I would like to add 8 1.8Tb SAS disk in RAID5 with one spare disk. How can I condifure it?

I am not clear the A and B pool, what does it mean?

Can I configure the spare disk which is relted to the new disk group? Or is it a global spare disk?

Thanks.

[support_s]

System recommended content:

1. MSA2050 - Disk-Group in QTOF after moving disks from MSA 2050 to MSA2040

2. HPE MSA 2050 User Guide

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[adam900331]

Thanks. I have already read this, but unfortunatelly not clear for me.

Global spare: How its work when there is different type of drive (SAS 1.2Tb, SSD 1Tb, SAS,1.8Tb)? If the SAS 1.8Tb drive is spare, what happend when SAS 1.2Tb or SSD 1Tb disk has fault? Is the global spare related to the all of the disk or only disk group?

Thanks.

[JonPaul]

@adam900331 

Thanks for the information, makes it clearer from your other post.
A 1.8TB SAS drive will be compatible spare for and Enterprise SAS (10k/15k) in the system which is 1.8TB or smaller.  If a 1.2TB 10k Enterprise SAS drive would have a fault, the 1.8TB drive will be used for reconstruct.
There is no way in the MSA 2050 to dedicate a drive for a specific disk-group.  All spares are Global Spare and can be used for any fauted drive of the same type (SSD, Enterprise SAS 10k/15k or MDL-SAS 7.2k)

Putting a disk-group of 1.2TB SAS drives in the same Pool as a disk-group of 1.8TB drives would not be a best practice.  The data within the pool will be balanced between the disk-groups with the 1.2TB disk-group eventually filling while the 1.8TB Disk-group will still have available capacity. At that point ALL new I/O would go to the 1.8TB disk-group and could lead to inconsistent performance.  
Volumes are what are presented to hosts.  The volumes are a portion of a Pool (A or B). It looks like the initial setup of your MSA segregated volumes for the SSD capacity on Pool B from volumes for the Enterprise SAS 1.2TB drives on Pool A.  Any new volumes could be part of either of these pools selected at the time the new volume is created.  If you add the 1.8TB drives to Pool A then you create a 'wide-stripe' on the Tier where volumes would be partially on the 1.2TB drives and partially on the 1.8TB drives.  The MSA Tiering engine will determine where volume data resides but both disk-groups would have roughly the same performance until the larger disk-group was the only one with capacity.  If you add in the 1.8TB disks to Pool B would the pool then balances volume data between the SSD tier and the Enterprise SAS tier.  The Tiering Engine again would make the decisions on which parts of which volumes resided on SSD and Enterprise SAS.  The decision is determined by data utilization, the most accessed data will reside on SSD and the lesser accessed data on Enterprise SAS.