On Sat, Jan 16, 2010 at 4:16 PM, Michael Fischer <[email protected]>wrote:
> On Sat, Jan 16, 2010 at 4:10 PM, David Birdsong > <[email protected]>wrote: > >> On Sat, Jan 16, 2010 at 3:55 PM, Michael Fischer <[email protected]> >> wrote: >> > This scheme seems very baroque. Why not just reduce the size of your >> caches >> > so you don't page-thrash and let Varnish's builtin LRU algorithm handle >> the >> > eviction? >> >> Then I wont be able to cache nearly as much. I want to originate as >> much content as possible on the varnish servers ie. reduce backend >> fetches. There is no way I could fit any useful amount of my working >> set into a storage that could handle the evictions without spending an >> unreasonable amount of money (basically fit it in RAM.) -I'd love to >> be proven wrong though. As far as random reads go, the SSD's are >> really good; it's just the writes that kill me. >> >> Right now a mostly filled cache server with ~80-160GB allocated can >> maintain between 90-92% cache hit ratio at 400-500Mb/sec. When it >> fills up completely eviction cause the machine to keel over, parent >> can't ping the child, health checks fail -general badness. I'd like >> to let the eviction run under supervision (automated supervision) and >> augment the eviction such that it buys back a few hours not minutes. > > > What OS are you running? This might be one of those rare cases where a > little more "swappiness" (i.e., aggressiveness of the pageout algorithm) > might buy you something. > This page may be useful if you're running on Linux: http://www.westnet.com/~gsmith/content/linux-pdflush.htm --Michael
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