High Availability (Was Re: fsck is dead)

Sean Hunter (sean@uncarved.co.uk)
Sat, 3 Jul 1999 09:29:24 +0100

In my experience with a number of very large banks etc, when people
need mission-critical fault-tolerant systems, they use a complete
hardware/OS/software solution such as tandem. For normal high
avaliability, something like a unix H/A pair (such as two suns) is
very common.

If you think fsck time is a factor in the equation then your H/A
solution is almost certainly inadequate to your needs. Only a
slahdotter would think that an ftp server had a mission-critical H/A
requirement. Think about swift message servers (where every message
is a direct transfer of funds), think about settlement systems (which
settle transactions worth sometimes hundreds of millions), and think
about trading systems. For example, I worked in a bank where someone
forgot to send a fax confirmation and it cost the bank £1000000.

fsck time isn't a consideration in these sorts of settings. Its much
more important in the more common case where you just want your
web/ftp/quakeserver up asap.

Sean Hunter

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