Fedora 19 - filesystems slow

[Heinz Diehl]

On 02.07.2014, Rick Stevens wrote: 

> I don't know of a way to control either the size of the cache or its
> retention period. It might be controllable via a sysctl, but I've never
> tried to bugger things like that.

Look at parameters which can control the kernels virtual memory
management, e.g.:

vm.dirty_background_ratio
vm.dirty_background_bytes
vm.dirty_ratio
vm.dirty_bytes
vm.dirty_writeback_centisecs
vm.dirty_expire_centisecs

If you can reproduce the "slow" disk behaviour by dropping the caches,
maybe you'll gain some advantage by tweaking some of those.

echo 3 > /proc/sys/vm/drop_caches

I for myself have been using

 vm.swappiness = 10
 vm.dirty_ratio = 10
 vm.dirty_background_ratio = 5

for a long time, avoiding long stalls when writing dirty pages to
disk.