[Haskell-cafe] Parallel weirdness
Brandon S. Allbery KF8NH
allbery at ece.cmu.edu
Sat Apr 19 12:31:44 EDT 2008
On Apr 19, 2008, at 11:53 , Murray Gross wrote:
> 2. You need to account for I/O buffering (not only by your OP
> system in RAM, but by your disk controller)--after the first set of
> I/O operations, your data may be in buffers, so subsequent uses may
> retrieve data from buffers rather than from the disk itself.
> Similarly, you also have to take into account paging and cache
> issues, which could make the first run much slower than immediate
> subsequent runs.
Note also that, unless you use SCSI or very high-end SATA drives,
they ignore requests to disable buffering. (References on request,
you can probably find them by poking around http://www.pdl.cmu.edu/.
Short summary: consumer drives are optimized for benchmarks, not for
data safety. This is why early 32-bit Windows releases often lost
data on shutdown until the shutdown was modified to sleep for 10-15
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university KF8NH
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