Hi, since SAPDB does not use any feature of a filesystem for its volumes(alias devspaces) any kind of filesystem overhead including a buffer cache is just an overhead. SAPDB opens using O_SYNC, but O_DIRECT is not yet used. All Read/Write activity use Systempages which are aligned to 4KByte. The LINUX raw devices which are preferred are those 'unbuffered' /dev/raw/rawX. CU jrg
> -----Original Message----- > From: Martin [mailto:mrogge@;froggy.com.au] > Sent: Samstag, 2. November 2002 05:54 > To: [EMAIL PROTECTED] > Subject: definition of term "raw device" > > > Hi, > > it has occurred to me that the term "raw device" can be > interpreted in > different ways under linux. There are buffered block devices > like /dev/hda, > /dev/scd0 etc. and in later kernels unbuffered devices like > /dev/raw/raw1 > etc. that may be bound to the same hardware. Those unbuffered devices > require a 512 byte alignment for memory and disk access. > > My question: can SAPDB use unbuffered devices for dev spaces, > and is it > advisable to use them? Thanks, > > cu Martin > _______________________________________________ > sapdb.general mailing list > [EMAIL PROTECTED] > http://listserv.sap.com/mailman/listinfo/sapdb.general > _______________________________________________ sapdb.general mailing list [EMAIL PROTECTED] http://listserv.sap.com/mailman/listinfo/sapdb.general
