I'm running into a maximum throughput issue here and need some advice on which way to tune my knobs. We're running a 10Gbit fileserver for backup distribution. It's a two disk S-ATA2 setup on an LSI MegaRAID Controller. The server also got 24gig of memory.
We have a need to mirror our last uploaded backup with maximum throughput.
The RAID0 for our "hot" backups gives us around 260 MB/sec write and 275 MB/sec read. A tested tmpfs with size 20GB gives us around 1GB/sec. This kind of throughput is what we need.
Now how can I tune the virtual memory subsystem of Linux to cache the last uploaded files for as long as possible in memory without writing them out to disk (or even better: writing to disk AND keeping them in memory)?
I setup the following sysctls, but they dont give us the throughput we expect:
# VM pressure fixes vm.swappiness = 20 vm.dirty_ratio = 70 vm.dirty_background_ratio = 30 vm.dirty_writeback_centisecs = 60000
This should in theory give us 16GB for caching I/O and wait some minutes until its writing to disk. Still when I benchmark the server I see no effect on writing, the throughput doesnt increase.
Help or advice needed.