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    SubjectRe: Warning - running *really* short on DMA buffers while doing file transfers
    >     I reported this same problem some weeks ago -
    > http://marc.theaimsgroup.com/?l=linux-kernel&m=103069116227685&w=2 .
    > 2.4.20pre kernels solved the error messages flooding the console, and
    > improved things a bit, but system load still got very high and disk read
    > and write performance was lousy. Adding more memory and using a
    > completely different machine didn't help. What did? Changing the Adaptec
    > scsi driver to aic7xxx_old . The performance was up 50% for writes and
    > 90% for reads, and the system load was acceptable. And i didn't even had
    > to change the RedHat kernel (2.4.18-10) for a custom one. The storage was
    > two external Arena raid boxes, btw.

    I would be interested in knowing if reducing the maximum tag depth for
    the driver improves things for you. There is a large difference in the
    defaults between the two drivers. It has only reacently come to my
    attention that the SCSI layer per-transaction overhead is so high that
    you can completely starve the kernel of resources if this setting is too
    high. For example, a 4GB system installing RedHat 7.3 could not even
    complete an install on a 20 drive system with the default of 253 commands.
    The latest version of the aic7xxx driver already sent to Marcelo drops the
    default to 32.

    --
    Justin

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