Can I improve initial read performance

[Arsenio B. Talingdan]

I have a 20 gig file on stiped JBODs. The sequential read speed is 160+ megs per second if the same buffer (4megs) is used over and over. If I try and read the entire file into memory, the read speed is 100 megs per second probably because of the time it takes the system to map and clear my 20 gig allocated area. If I page touch all the pages in the 20 gigs first, my speed is back to 160 but my total time is the same.

I am on a 7410 with 32 gigs using direct I/O. Is there any way to improve the speed by which the system prepares my memory for the I/O? I have the same problem with an XP128 on a 8400.

[Don Capps_1]

When one is using Direct I/O the system is not performing any read-ahead. If one uses large transfer sizes this helps. If one uses large transfer sizes and POSIX async I/O (to create your own read-aheads) this helps too. If one is using stripes then it helps to stripe across controllers too.

[James Beamish-White]

Take a look at the throughput section of http://www.hp-partners.com/msc_public/html/technical_support/nastran750tuning.htm, relating to dbc_pct_max. It may be of some help.

Cheers!
James
-going for graduation ;-)