On Fri, 29 May 2009, Tom Limoncelli wrote: > On Fri, May 29, 2009 at 3:31 PM, <[email protected]> wrote: >> on the other hand, for server uptime outside of maintinance, you can buy >> commodity hardware that will run for years without any failures (your >> upgrades are during the allowed maintinance), but you can have another box >> of the same type that fails in a month, so you still need to have the >> service be HA. if things go well you drasticly exceed your SLA, but if you >> removed the redundancy you run a very real risk of drasticly failing to meet >> your SLA with a single incident. how do you account for this? > > I wouldn't remove the redundancy completely but getting the right > amount of redundancy is more economical.
this sounds much more reasonable than what it sounded like you said initially. > Example 1: You have 2 redundant servers so that one can go down and > the other will take over. Do you both also need expense RAID > controllers? Would software mirroring be sufficient and cheaper? or for that matter, do you need raid at all? (can you just say that when one drive dies you failover to the other box) however note that expensive raid controllers frequently include a significant amount of cache, and that can be a _significant_ perfomance difference over raw drives for writes and fsyncs. for most of my systems, I don't do raid if the box in in a HA setup (the exception being the boxes who's purpose for existing is to archive data) David Lang _______________________________________________ Discuss mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/discuss This list provided by the League of Professional System Administrators http://lopsa.org/
