nbdkit-noextents-filter - disable extents in the underlying plugin
nbdkit --filter=noextents plugin
“Extents” are a feature of the NBD protocol / nbdkit which allow the client to detect sparse regions of the underlying disk.
nbdkit-noextents-filter disables this so that the plugin appears to be fully allocated, at least to a client that requests structured replies. It is also possible to use the --no-sr option to nbdkit to prevent the client from using structured replies, which among its other side effects will prevent the client from querying extents at all.
This filter can be useful when combined with nbdkit-file-plugin(1) serving a file from a file system known to have poor
lseek(2) performance (
tmpfs is known to be one such system).
There are no parameters specific to nbdkit-noextents-filter. Any parameters are passed through to and processed by the underlying plugin in the normal way.
nbdkit --dump-config to find the location of
nbdkit-noextents-filter first appeared in nbdkit 1.14.
nbdkit(1), nbdkit-filter(3), nbdkit-extentlist-filter(1), nbdkit-fua-filter(1), nbdkit-multi-conn-filter(1), nbdkit-nocache-filter(1), nbdkit-noparallel-filter(1), nbdkit-nozero-filter(1), nbdkit-file-plugin(1).
Richard W.M. Jones
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