I need to speed up slow, large storage with local SSD drive. I figured out I could do this with union filesystems. Here are results with nginx reading data from:
- local SSD alone: ~140 transactions/s.
- large-slow storage alone: ~25 transactions/s
- local SSD aufs-mounted with local dir and empty dir: ~30 transactions/s
- local SSD aufs-mounted with local dir and large-slow storage dir: ~30 transactions/s
- local SSD overlayfs-mounted with local dir and large-slow storage dir: ~140 transactions/s
As you can see, my bottleneck is aufs. Overlayfs with local+large-slow storage can be as fast as local harddrive but this is because it doesn't allow underlying filesystem to change (so it doesn't suit me).
Do you have any other ideas how to solve this problem?