On Wed, 2012-03-07 at 10:12 +1300, Jim Cheetham wrote: > On Wed, Mar 7, 2012 at 2:26 AM, Kent Fredric <[email protected]> wrote: > > On 6 March 2012 12:36, Adrian Mageanu <[email protected]> wrote: > >> Yes, disk I/O mostly due to furious swap when available RAM is exceeded, > >> and then there is the 100% of every available CPU, that's when keyboard > >> and mouse get locked and the fans screm mad. > > Swap is overrated. These days we have sufficient RAM to keep the OS > running properly, and when machines descend into swap the machine > generally dies because we overcommit and have slow disks. Switch off > swap, and let the OOM killer do its job - on a well-run server a > critical service should be restarted by init anyway ... > > $ free > total used free shared buffers cached > Mem: 8149024 7968776 180248 0 192868 4736620 > -/+ buffers/cache: 3039288 5109736 > Swap: 0 0 0 > > More of this philosophy is touched on during Anthony Town's recent > LCA2012 presentation : > http://www.youtube.com/watch?v=p_u6BDFkybE > > -jim
You're suggesting that it's OK to let the system kill off critical processes?? That's a bit of a DJB approach imo... What if that process removes all connectivity with said server? And said server is hosted in Guatemala? And the hosting provider has no staff to support you until Monday morning? Yes, this has happened to me ( Well, it was Canada, but I like typing Guatemala... ). Suffice to say I no longer use them ( I've listened to recommendations, and now almost exclusively use linode for international sites ) but that's by the by. It is very annoying and difficult to plan for a swapless scenario - there's (at least) one local VPS provider that does this, and setting the server up, creating alarms all over the place just to be sure you can cope is a real PITA. You can easily end up with services that say they're up and running when they're stuffed, so just using inittab is no good - you end up using ping/pong type programs just to check they really are up. More overhead, more testing... generally more grief. My big gripe is this. I'm typing this on my new workstation. The memory cost $50 for 8GB. Why doesn't everyone just stuff servers as full as possible, with the intention of never using swap, but having it there just in case. This is extremely useful, for example when commissioning a new server, and you need to tune your guesstimate config to what's really required. My $0.02, Steve -- Steve Holdoway BSc(Hons) MNZCS <[email protected]> http://www.greengecko.co.nz MSN: [email protected] Skype: sholdowa
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