Myron, On 4/9/06 1:18 PM, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote:
> I am working with Solaris on SPARC almost exclusively and I believe Josh said > that Sun was the one who found the bursty behavior with scans. Has it been > confirmed that this is the case on all/most platforms? It was our folks at Greenplum that found this behavior. It is particularly bad on Solaris because of the poor OS readahead on UFS. You can modify UFS readahead behavior using OS tuning parameters as mentioned previously in the thread and contained in Jignesh Shaw's blog at Sun (we worked with Jignesh and Sun for about a year to get this information). Interestingly, the use of POSIX fadvise() to indicate the nature of the I/O as sequential makes a big positive difference in many cases, but it hurts a lot in some other workloads where there is seek I/O and the sequential pattern was set. I think the best solution will use a more direct overlap approach in the executor. - Luke ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly