>So you are saying that the entirety of swap at highest >priority was filled and you ran out of swap or what, >exactly?
With different priorities, at SLES7, we found that Linux would go into a loop and lock out all other tasks after the first swap with highest priority filled. This was at the RC6 level. It may have been fixed in the RC7a level and we have not seen the problem since SP1 was applied. Nor have we seen the problem with SLES8. We routinely run with 4 real 3390-3 swaps on RVA and we have pushed Linux to 22 swaps. (Both are volume test workloads). Since they are all on comparable devices, we set them at the same priority and I/O is balanced across all devices. It seems to me with a hierarchical swap structure (starting with the fastest as highest priority and going down to the slowest) that each time you fill a faster device then when your slower device kicks in, the is a disportinate decrease in performance. I suppose I would only use this scenario if I infrequently used the lower priority, slower device, using it as a safety valve, as it were. If I had a consistent paging load because of memory constraints, I would prefer that my swapping devices were at the same priority (relatively high) so that the I/O would be evenly distributed over the devices and a page-in would get decent service. (It would be nice if Linux changed the names to "paging", their real function, rather than "swapping", so the discussion doesn't have to drift between "swap devices" and "paging load". But then again, if wishes were fishes ... ;-) ). ===== Jim Sibley RHCT, Implementor of Linux on zSeries "Computer are useless.They can only give answers." Pablo Picasso __________________________________ Do you Yahoo!? Yahoo! Finance: Get your refund fast by filing online. http://taxes.yahoo.com/filing.html
