05-05-2009
Quote:
Originally Posted by
otheus
But maybe there was a random fuzz factor involved.
Exactly this was the case and it is one of the great ideas of IIRC Bob Metcalfe to have done so. The "fuzz factor" was a random number by which the increasing number was multiplicated. Thus two colliding nodes probably weren't colliding at their next try, because the randon numbers would be most probably different.
"Pure" ALOHA (the first CSMA network) without timeslots operated at a ~18% throughput / raw bandwith ratio, whereas "slotted" ALOHA (with timeticks) roughly doubled that efficiency. Ethernet (the successor of ALOHA) had an even higher efficieny.
bakunin
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LEARN ABOUT CENTOS
btrfs-image
BTRFS-IMAGE(8) System Manager's Manual BTRFS-IMAGE(8)
NAME
btrfs-image - create/restore an image of the filesystem
SYNOPSIS
btrfs-image [options] source target
DESCRIPTION
btrfs-image is used to create an image of a btrfs filesystem. All data will be zeroed, but metadata and the like is preserved. source is
the special file corresponding to the device containing a btrfs filesystem. (e.g /dev/sdXX). target is the image file that btrfs-image
creates. When used with -r option, btrfs-image restores the image file from source into target.
OPTIONS
-r restore metadump image.
-c value
compression level (0 ~ 9).
-t value
number of threads (1 ~ 32) to be used to process the image dump or restore.
-o use the old restore method, this does not fixup the chunk tree so the restored file system will not be able to be mounted.
-s Sanitize the file names when generating the image. One -s means just generate random garbage, which means that the directory indexes
won't match up since the hashes won't match with the garbage filenames. Using -ss will calculate a collision for the filename so
that the hashes match, and if it can't calculate a collision then it will just generate garbage. The collision calculator is very
time and CPU intensive so only use it if you are having problems with your file system tree and need to have it mostly working.
-w Walk all the trees manually and copy any blocks that are referenced. Use this option if your extent tree is corrupted to make sure
that all of the metadata is captured.
AVAILABILITY
btrfs-image is part of btrfs-progs. Btrfs is currently under heavy development, and not suitable for any uses other than benchmarking and
review. Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for further details.
SEE ALSO
btrfsck(8),mkfs.btrfs(8)
BTRFS-IMAGE(8)