On Thu, Sep 16, 2004 at 07:04:52PM -0400, David Boyes wrote: > > We are on STK V2X DASD array. We can do very well without Linux adding > > further caching. Is there a way to tell Linux not to cache the DASD? > > AFAIK, there's no way to turn caching completely off in Linux. You can > reduce the amount of storage Linux uses for caching by reducing the size > of the LPAR (which will have other negative effects), but there still > will be some caching going on.
Thats true. But you can influence the cache behaviour. I use the following parameters for /proc/sys/vm/bdflush on a 2.4.21 Kernel: s390z06:/proc/sys/vm # uname -a Linux s390z06 2.4.21-250-default #1 SMP Wed Sep 22 09:03:27 UTC 2004 s390x unknown s390z06:/proc/sys/vm # cat bdflush 5 5000 0 0 100 500 80 5 0 The parameter have the following meening: 5 - start writing if more than 5% of the buffers are dirty 5000 - maximum number of buffer to write in one wakeup 0 - dummy 0 - dummy 100 - number of ticks for wakeup (if HZ is 100 this means 1 sec) 500 - number of ticks a buffer may wait before written 80 - start synchronous write if more than 80% of the buffers are dirty 5 - dummy 0 - dummy With these parameters the system starts writing earlier and I/O peaks happen less often. to view the result start vmstat 5 500 and look for the coloums bi and bo Ihno -- "Never trust a computer you can lift." -- Ihno Krumreich [EMAIL PROTECTED] SuSE Linux AG Projectmanager S390 & zSeries Maxfeldstr. 5 +49-911-74053-439 D-90409 N�rnberg http://www.suse.de ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
