P7 740 E6C EXP24S mode 1, disk upgrade options

Currently have 18 177 SSD in a 5887 EXP24S mode 1 , with dual 5913.
CEC already used for other LPAR, and I would not use CEC for Prod.
Would like to add disks, either SSD and/or HDD.

From what I read, you cannot mix SSD capacities and/or HDD in a 5887, so a 2nd EXP24S would be required, if I keep existing 18 SSD.

It also appears that including disk units in an existing parity set is no longer an option for Power8 foward and is not recommended for newer generation SAS RAID adapters.
"Including disk units into an existing parity set with PCIe2, PCIe3, and newer generations of SAS RAID adapters can result in a large performance degradation"

1) I could add 6 177 SSD, but not much gain in storage, only a short term solution.
2) Replace existing 177 SSD with 775 SSD, very costly, but would be good for long term.
3) Add HDD for cold data, using QAEZDISK from RTVDSKINF, I ran some queries to analyze hot/cold data based on last use date, about 50/50 out of 2.8 TB.
Adding a few HDD for 1.2 TB of cold data hardly seems worth the hassle of a 2nd EXP24S, along with running STRASPBAL *USAGE on a constant basis.

Another concern is the age of the 5887 EXP24S GEN2. Announced 4/12/11, will be 4 years old.
Also, the 775 SSD GEN 3 were announced 10/7/2013, 15 months old.
Reviewing IBM announcement history, I suspect both a new IO drawer and larger SSD drive maybe around the corner, 1st qt 2015.
If and when announced, will it be supported on a P7 740 E6C?, maybe P8 only.
I'm really frustrated with this decision, not many good IO options available.

Thank You
_____
Paul Steinmetz
IBM i Systems Administrator

Pencor Services, Inc.
462 Delaware Ave
Palmerton Pa 18071

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