Sue,

Never mind, I found an old note you sent me back 2014, I'm sure the same rules still apply.

If creating 1 new parity set puts you in the position of having an odd number of parity sets, this could cause an imbalance for the controllers which could create performance anomalies.

I now need to determine if 7 SSD will be enough (3.1 TB) or do I need 9 (4.6 TB) ; losing 2 drives to parity + 1 hot spare.


Paul

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Steinmetz, Paul
Sent: Wednesday, December 02, 2015 10:11 AM
To: 'midrange-l@xxxxxxxxxxxx'
Subject: RE: Power8 S824 - mixing/placement SSD/HDD - is 571 gb 15K largest HDD drive available

Sue,

Would it be acceptable to have only 1 parity set of 5 with 1 hot spare for the CEC SSD controlled by the EJOP backplane?

Paul

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Sue Baker
Sent: Tuesday, December 01, 2015 1:11 PM
To: midrange-l@xxxxxxxxxxxx
Subject: RE: Power8 S824 - mixing/placement SSD/HDD - is 571 gb 15K largest HDD drive available

"Steinmetz, Paul"
<PSteinmetz@xxxxxxxxxx> wrote on
Tue, 01 Dec 2015 06:13:37 GMT:

I was planning on filling the EXP24S with 24 ESFS - 1.7TB 10K
RPM SAS SFF-2 Disk Drive 4 k Block (IBM i) Lose 2 to
parity, 1 to hot spare - 36 TB usable, ASP # 2, mostly cold data. For
the CEC, I was planning on 6 (or more) ESOP - 775GB
SFF-3 4k SSD for IBM I , Lose 1 to parity, 1 to hot spare -
3.1 TB usable, this would be SYS ASP 1, containing load source, Q
libs, development tools, 1 copy of development data.
All controlled by 2 - EJ0L PCIe3 12GB Cache RAID SAS Adapter


Paul, all 10K in EXP24S behind EJ0L is fine. You're planning for 2 arrays, which is also good.

The CEC drives have the high function backplane (EJ0P) which is
2 IOAs on the planar and will not be controlled by the EJ0L.
You should plan for 2 arrays for these drives too. I would opt for 7 SSDs to accommodate 2 arrays + 1 hot spare or 9 SSDs to do the same.

--
Sue
IBM North America Advanced Technical Sales Support (ATS) Power Systems Rochester, MN

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