On Feb 2 2008 12:23, Pavel Machek wrote: >On Fri 2008-02-01 14:25:32, Laurent Vivier wrote: >> This patch allows Network Block Device to be mounted locally. > >What is local nbd good for? Use loop instead...
Local NBD is good for when the content you want to make available through the block device is dynamic (generated on-the-fly), non-linear or supersparse. Take for example VMware virtual disks. Just a guess, but they roughly can look like this: kilobytes 0.. 1: header kilobytes 1..10: correspond to LBA 0..20 kilobytes 11..20: correspond to LBA 40..60 kilobytes 21..22: correspond to LBA 22..23 So what we have is non-linearity -- LBA 22 comes after LBA 40 -- loop does not deal with that. And there is supersparsity -- the VMDK file itself is complete, but unallocated regions like LBA 24..40 are sparse/zero when projected onto a file/block device, respectively; loop cannot deal with that either. In fact, VMware uses local nbd today for its vmware-loop helper utility, most likely because of the above-mentioned reasons. (Though it quite often hung last time I tried.) ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Nbd-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/nbd-general
