RO filesystems can be bad, but usually they're soft failures for us: * Memcache can still work just fine * Db servers stop responding (and the app handles that fairly gracefully) * Web servers serve files from a RAM disk, so they keep working

No reason against 10G copper specifically - we haven't had to address the problem in detail yet. When we do, we might choose copper. Depends what happens when it happens :-)

We had a very nasty incident a few months ago, where the drive in one of the LDAP servers died. Well, it sort-of died. It started to time out a lot but didn't go fully offline. openldap kept running, but when you connected to it, the TCP connection would open and hang. This meant that all of our servers saw the server as "OK", but LDAP stopped working and caused all kinds of brilliant havoc :-)