January 20th, 2012

The magical key!

Dear Diary,

today the IOPS-unlocking FastPath key arrived for the LSI MegaRAID 9265-8i card arrivied!  I was so excited, until I opened the box an found what’s basically something that short-circuits two headers on the RAID card.

What a rip-off.  It probably disables some sleep(1) calls in the firmware on the card.

Anyway, I plugged it in, and did the benchmarks, and I got…  absolutely no (zero, zip) difference.  No difference whatsoever.  Zilch.  Nada.

So I googled around a bit, and found someone who claimed that the RAID card should be configured as write-through, no read-ahead, direct I/O to make the FastPath stuff be all awesome and stuff.

I did that.  Annoyingly enough, there seems to be no way to just flip those settings without rebuilding the RAID, so testing takes a while.

And benchmarking afterwards shows that…  throughput drops to one fifth of the standard settings, and random reads of files is absolutely no faster.

I have no more time for benchmarking, since I have to go to Rome.  Diary, I’ll continue fiddling with the RAID card when I get back.

But the strangest thing has happened.  I was looking through some of the previous pages in my secret diary, and I found that somebody else has been making comments!  How is that possible!?  Are other people able to read my diary?  Is Google betraying my secrets to the world?

Anyway, the comment said that I should perhaps just use the SATA 2.0 connectors on the motherboard to see what IOPS I get without using the MegaRAID card.  That makes tons of sense, because I don’t know whether the lack-lustre random read performance I’m getting is because of the disks or the RAID card.

I’ll do that when I get back in about four weeks. 

And I’ll see whether I can secure my diary further somehow.

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