load balancing at fastmail.fm

[Rob Mueller]

> Thanks, that was interesting reading.
> Is there any specific reason you didnt opt for a cluster filesystem?

Internal knowledge mostly. We very were familiar with the performance and 
overall usage implications of a local filesystems on locally attached 
SATA-to-SCSI RAID boxes that we've been using for a while.

The setup, performance, maintenance, etc of cluster filesystems would 
involve learning and using entirely new technologies we didn't know much 
about, are complex, and probably don't trust fully. In high usage 
environments like we have, it stresses software and finds bugs you don't 
expect. Our backup system was crashing our kernel NFS server regularly in 
mutliple versions of the linux kernel. Even when we tried LVM once we 
managed to find subtle bugs that seemed to cause filesystem corruption 
(search for LVM reiserfs corruption, there's old reports in kernel mailing 
lists). These are both supposedly well tested, well used and understood 
technologies that when you push them still show their corner case problems. 
I'd hate to see cluster filesystems pushed given their inherent complexity.

Rob