2011-06-17 15:06, Edward Ned Harvey пишет:
When it comes to reads: The OS does readahead more intelligently than the
disk could ever hope. Hardware readahead is useless.
Here's another (lame?) question to the experts, partly as a
followup to my last post about large arrays and essentially
a shared bus to be freed ASAP: can the OS request a disk
readahead (send a small command and release the bus)
and then later poll the disk('s cache) for the readahead
results? That is, it would not "hold the line" between
sending a request and receiving the result.
Alternatively, does it work in a packeted protocol (and in
effect requests and responses do not "hold the line",
but the controller must keep states - are these command
queues?), and so the ability to transfer packets faster
and free the shared ether between disks, backplanes
and controllers, is critical per se?
Thanks,
//Jim
The more I know, the more I know how little I know ;)
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