Maciej Jan Broniarz ha scritto:
W dniu 10-04-05 22:08, Tonix (Antonio Nati) pisze:
Maciej Jan Broniarz ha scritto:
W dniu 10-04-05 17:45, Mike Jakubik pisze:
>
Just to use exact words, fault toulerancy is not possible with any
FreeBSD/Linux O.S.
F.T. means outage can occur in every moment, but all current operation
will be always completed by other equipments; so there will not be
interrupted/lost operations.
Hmm. Thanks for the tip. Which *NIX os can be used to build an FT
solution then? Solaris? AIX? HP-UX?
For a FT solution you need usually an hardware solution, very expensive.
Server must have all doubled, with custom chips for checking if parts
are working (and which part is broken, which may not be easy to understand).
VMware claims to have a software fault toulerant solution, syncronizing
two servers in real-time, but I don't know the efficiency.
The most ISP use HA solutions, which are ok for the most of WEB/e-mail
operations.
Operations are not available for a few milliseconds/seconds, depending
on the architecture you use.
Just to complete, drbd+heartbeat are NOT FT. They are HA. When the
master server goes down, backup server must acknowledge the new status,
then mount the replicated disk (think to disk check!), then start
services working on that disk. So this solution needs a lot of
seconds, probably minutes to work.
With a good carp architecture, you just need milliseconds.
Tonino
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