Facebook Flashcache

I now have a new Crucial M4 SSD (256 GB) to play with, so I set it up using FaceBook flashcache. It took a little while to figure out how to cache the root filesystem (I only have one large partition including), but it seems to work great.

I did some 50 GB benchmarks with bonnie++ and it seems like flashcache with an SSD + a 7200 RPM 1 TB SATA disk is *faster* for some tasks than pure SSD. I’m not sure why this is. If I had the patience to do a test that was larger than cache, I suspect these results would be different.

My results can be seen below:









Version 1.96Sequential OutputSequential InputRandom
Seeks
Sequential CreateRandom Create
SizePer CharBlockRewritePer CharBlockNum FilesCreateReadDeleteCreateReadDelete
K/sec% CPUK/sec% CPUK/sec% CPUK/sec% CPUK/sec% CPU/sec% CPU/sec% CPU/sec% CPU/sec% CPU/sec% CPU/sec% CPU/sec% CPU
SATA TEST50000M92496861577289264384476958339101.54161783619++++++++2395517++++++++++++++++++++++++
Latency14922us801ms1010ms81197us539ms5584msLatency325us450us491us345us13us468us
SSD test50000M68399193744187696810364298226455214416150161675217++++++++2549418++++++++++++++++++++++++
Latency15995us426ms677ms3442us14819us1741msLatency313us398us2110us395us20us542us
facebook flashcache test50000M101399199640157713615471796208983352686136162164924++++++++++++++++++++++++++++++++++++++++
Latency14218us316ms949ms6500us144ms1206msLatency283us366us458us293us63us446us

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