* stripe_cache_size ? @ 2005-12-09 8:44 Kyle Wong 2005-12-09 9:47 ` Neil Brown 0 siblings, 1 reply; 5+ messages in thread From: Kyle Wong @ 2005-12-09 8:44 UTC (permalink / raw) To: linux-raid Hi, I found that there's a new sysfs "stripe_cache_size" variable. I want to know how does it affect RAID5 read / write performance (if any) ? Please cc to me if possible, thanks. Kyle ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: stripe_cache_size ? 2005-12-09 8:44 stripe_cache_size ? Kyle Wong @ 2005-12-09 9:47 ` Neil Brown 2005-12-09 14:06 ` Bill Davidsen 0 siblings, 1 reply; 5+ messages in thread From: Neil Brown @ 2005-12-09 9:47 UTC (permalink / raw) To: Kyle Wong; +Cc: linux-raid On Friday December 9, kylewong@southa.com wrote: > Hi, > > I found that there's a new sysfs "stripe_cache_size" variable. I want to > know how does it affect RAID5 read / write performance (if any) ? > Please cc to me if possible, thanks. Would you like to try it out and see? Any value from about 10 to a few thousand should be perfectly safe, though very large values may cause the system to run short of memory. The memory used is approximately stripe_cache_size * 4K * number-of-drives NeilBrown ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: stripe_cache_size ? 2005-12-09 9:47 ` Neil Brown @ 2005-12-09 14:06 ` Bill Davidsen 2005-12-09 20:43 ` Neil Brown 0 siblings, 1 reply; 5+ messages in thread From: Bill Davidsen @ 2005-12-09 14:06 UTC (permalink / raw) To: Neil Brown; +Cc: Kyle Wong, linux-raid On Fri, 9 Dec 2005, Neil Brown wrote: > On Friday December 9, kylewong@southa.com wrote: > > Hi, > > > > I found that there's a new sysfs "stripe_cache_size" variable. I want to > > know how does it affect RAID5 read / write performance (if any) ? > > Please cc to me if possible, thanks. > > Would you like to try it out and see? > Any value from about 10 to a few thousand should be perfectly safe, > though very large values may cause the system to run short of memory. > > The memory used is approximately > stripe_cache_size * 4K * number-of-drives What??? I hope that's a typo... 1 - there's no use of the sysfs variable? 2 - that's going to be huge, 128k * 4k * 10 = 5.1GB !!! > > NeilBrown -- bill davidsen <davidsen@tmr.com> CTO TMR Associates, Inc Doing interesting things with little computers since 1979 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: stripe_cache_size ? 2005-12-09 14:06 ` Bill Davidsen @ 2005-12-09 20:43 ` Neil Brown 2005-12-12 20:51 ` Bill Davidsen 0 siblings, 1 reply; 5+ messages in thread From: Neil Brown @ 2005-12-09 20:43 UTC (permalink / raw) To: davidsen; +Cc: Kyle Wong, linux-raid On Friday December 9, tmrbill@tmr.com wrote: > On Fri, 9 Dec 2005, Neil Brown wrote: > > > On Friday December 9, kylewong@southa.com wrote: > > > Hi, > > > > > > I found that there's a new sysfs "stripe_cache_size" variable. I want to > > > know how does it affect RAID5 read / write performance (if any) ? > > > Please cc to me if possible, thanks. > > > > Would you like to try it out and see? > > Any value from about 10 to a few thousand should be perfectly safe, > > though very large values may cause the system to run short of memory. > > > > The memory used is approximately > > stripe_cache_size * 4K * number-of-drives > > What??? I hope that's a typo... > 1 - there's no use of the sysfs variable? 'stripe_cache_size' is the sysfs variable. Yes, it is used. > 2 - that's going to be huge, 128k * 4k * 10 = 5.1GB !!! That is why I warned to limit it to a few thousand (128k is more than a few thousand!). I just ran bonnie over a 5drive raid5 with stripe_cache_size varying in from 256 to 4096 in a exponential sequence. (Numbers below 256 cause problems - I'll fix that). Results: 256 cage,8G,42594,93,151807,38,50660,18,38610,91,172056,38,912.8,2,16,4356,99,+++++,+++,+++++,+++,4389,99,+++++,+++,14091,100 512 cage,8G,42145,92,186535,44,60659,21,42249,96,172057,37,971.9,2,16,4407,99,+++++,+++,+++++,+++,4452,99,+++++,+++,13909,99 1024 cage,8G,42250,92,210407,50,61254,21,42106,96,172575,37,903.1,2,16,4370,99,+++++,+++,+++++,+++,4395,99,+++++,+++,13809,100 2048 cage,8G,42458,92,229577,55,61762,21,41965,96,168950,36,837.9,2,16,4373,99,+++++,+++,+++++,+++,4460,99,+++++,+++,14084,100 4096 cage,8G,42305,92,250318,62,62192,21,42156,96,170692,38,981.8,3,16,4380,99,+++++,+++,+++++,+++,4426,99,+++++,+++,13723,99 Seq Write speed ^ Increases substantially. Seq Read ^ Doesn't vary much. Seq rewrite ^ improves a bit So for that limited test, write speed is helped a lot, read speed isn't. Maybe I should try iozone... NeilBrown ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: stripe_cache_size ? 2005-12-09 20:43 ` Neil Brown @ 2005-12-12 20:51 ` Bill Davidsen 0 siblings, 0 replies; 5+ messages in thread From: Bill Davidsen @ 2005-12-12 20:51 UTC (permalink / raw) To: Neil Brown; +Cc: Kyle Wong, linux-raid Neil Brown wrote: >On Friday December 9, tmrbill@tmr.com wrote: > > >>On Fri, 9 Dec 2005, Neil Brown wrote: >> >> >> >>>On Friday December 9, kylewong@southa.com wrote: >>> >>> >>>>Hi, >>>> >>>>I found that there's a new sysfs "stripe_cache_size" variable. I want to >>>>know how does it affect RAID5 read / write performance (if any) ? >>>>Please cc to me if possible, thanks. >>>> >>>> >>>Would you like to try it out and see? >>>Any value from about 10 to a few thousand should be perfectly safe, >>>though very large values may cause the system to run short of memory. >>> >>>The memory used is approximately >>> stripe_cache_size * 4K * number-of-drives >>> >>> >>What??? I hope that's a typo... >> 1 - there's no use of the sysfs variable? >> >> > >'stripe_cache_size' is the sysfs variable. Yes, it is used. > > > >> 2 - that's going to be huge, 128k * 4k * 10 = 5.1GB !!! >> >> > >That is why I warned to limit it to a few thousand (128k is more than >a few thousand!). > > Sorry, for some reason I read that as being in stripes instead of bytes, which would make it 128k for size only 2. My misread. >I just ran bonnie over a 5drive raid5 with stripe_cache_size varying >in from 256 to 4096 in a exponential sequence. (Numbers below 256 >cause problems - I'll fix that). > >Results: > 256 cage,8G,42594,93,151807,38,50660,18,38610,91,172056,38,912.8,2,16,4356,99,+++++,+++,+++++,+++,4389,99,+++++,+++,14091,100 > 512 cage,8G,42145,92,186535,44,60659,21,42249,96,172057,37,971.9,2,16,4407,99,+++++,+++,+++++,+++,4452,99,+++++,+++,13909,99 >1024 cage,8G,42250,92,210407,50,61254,21,42106,96,172575,37,903.1,2,16,4370,99,+++++,+++,+++++,+++,4395,99,+++++,+++,13809,100 >2048 cage,8G,42458,92,229577,55,61762,21,41965,96,168950,36,837.9,2,16,4373,99,+++++,+++,+++++,+++,4460,99,+++++,+++,14084,100 >4096 cage,8G,42305,92,250318,62,62192,21,42156,96,170692,38,981.8,3,16,4380,99,+++++,+++,+++++,+++,4426,99,+++++,+++,13723,99 > >Seq Write speed ^ >Increases substantially. >Seq Read ^ >Doesn't vary much. >Seq rewrite ^ >improves a bit > >So for that limited test, write speed is helped a lot, read speed >isn't. > >Maybe I should try iozone... > >NeilBrown > > > -- bill davidsen <davidsen@tmr.com> CTO TMR Associates, Inc Doing interesting things with small computers since 1979 ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2005-12-12 20:51 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2005-12-09 8:44 stripe_cache_size ? Kyle Wong 2005-12-09 9:47 ` Neil Brown 2005-12-09 14:06 ` Bill Davidsen 2005-12-09 20:43 ` Neil Brown 2005-12-12 20:51 ` Bill Davidsen
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