Ysul current hardware doesn't give satisfaction:
- zfs locks -- it's very common to wait for IO some seconds
- RAM too low
Decision has been made to supersede with a 32 or 64 Gb of RAM, pure SSD, raid 1 solution (some write performance cost is okay for redundancy). OS will be FreeBSD 11, with first the devserver role (we'll see afterwards what we do for webserver-legacy).