There was another interesting problem uncovered by my trying to read in most of my old floppy archive disks while I still could (!); cp *always* mmaps the input file. If there is a hard error on a slow device, the fact that the vnode-pager is doing the read makes the entire system hang. This is not desirable for floppies for 2 reasons: 1. they are slow. 2. they are error-prone. I suppose I could dd the whole floppy to a temp, then open it virtual. If that were done with conv=noerror,sync then (in many cases) one could recover as much data as could be recovered. That would be a fairly easy script, and would probably be faster than reading the files directly from the slow medium, at least if a full-track blocksize worked in the dd. However, it *would* be nice to have a flag to cp, or another similar command (I might be able to use cpio or tar in a pipeline?) that did ordinary reads and not mmap... (for that matter, there are devices (I suspect floppies are one of these, and I have seen hints that cdrom's are too) for which ordinary reads are much faster than mmap for whatever reason.) -- PeteReceived on Tue Jan 25 2005 - 20:31:23 UTC
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