Re: Will mixing 775 SSD and 177 SSD in a 5887 EXP24S I/O drawer be a potential performnace issue

"Steinmetz, Paul" <PSteinmetz@xxxxxxxxxx> wrote on Mon, 22 Dec
2014 03:39:18 GMT:

On a P7, 740 8205 E6C, I currently have 18 177 SSF-2 SSD (2844
gb; 5913 controllers) in a 5887 EXP24S I/O drawer, which is
100% of my production LPAR, CEC is not used for this LPAR. We
need to add disk for a few new PF and LF that will take a
large amount of DASD. I have 6 empty disk slots in a 5887
EXP24S I/O drawer. I was planning on adding 6 775 SSF-2 SSD
(3875 gb), one new RAID-5 parity set.

How manhy parity sets do you currently have? 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.

1) I could add these 6 drives to the current sys ASP.
These 6 drive would be accessed much more heavily because of
the large difference in size. Could this be a potential
performance issue, because these would be "hot drives"? "Hot
drives" with SSD would not be as noticeable as with spinny hot
drives.

The new SSDs have better performance than the old 177GB SSDs.
This may be enough to offset the effect of mixing the two SSD
sizes.

Or,
2) I could create a new ASP for these 6 drives, and then
place only these new files in this ASP. Still have the hot
drive issue, but less impact.

But now you have to manage files in different ASPs. This can
lead to complications for DB management, journaling, etc.

3) Are there other options??