[lug] Load-balancing web servers

[Sean Reifschneider]

On Fri, Jan 10, 2003 at 04:25:24PM -0700, Harris, James wrote:
>> think rsync-ing every 10 seconds is a viable solution, either...
>
>Check out http://www.it.uc3m.es/~ptb/nbd/ (Enhanced Network Block Device).
>It's supposed to be a much better implementation of network mirroring.

Yeah, but DRBD is supposed to be better for the job.  DRBD actually
encompasses the RAID and NBD functionality as a single entity, and can
do nice things like prefer the local device, pause the start-up of the
system/application until both machines are synced up, etc...

I've been using DRBD for just under a year now and it's been very
reliable for me.

NOTE: You can't use the file-system on both machines at once.  One
system is a master, one is a slave, and the slave keeps a copy of the
data, which you can't access until the master gets shut down.  It won't
help in this case.

For keeping two machines able to access the same data at the same time,
use something like GFS or (shudder) CODA.  These both will allow both
systems to access the same file-system at the same time.

Maybe doing an rsync every 10 seconds is not appropriate, but what about
once a minute?  It may be that you don't need something fancy after
all...

Sean
-- 
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Sean Reifschneider, Inimitably Superfluous <jafo at tummy.com>
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