nbdkit-cacheextents-filter(1)

📦
version 1.44.1 · 7 versions
, in opensuse-leap 16.0

💅 nbdkit-cacheextents-filter — cache extents

okay so this is the manual page for nbdkit-cacheextents-filter(1) from the nbdkit fam, and bestie… we gotta talk about it first. 🫶

⚠️ DEPRECATED ⚠️

Real talk first, because I love you: the cacheextents filter is deprecated in nbdkit ≥ 1.43.10 and will be removed in nbdkit 1.46. 😭

There is no direct replacement, but here's the thing — because this filter only ever worked for a narrow and unusual range of access patterns, it's likely that it has no effect on you and you can just… stop using it. 💀 periodt.

✨ SYNOPSIS ✨

nbdkit --filter=cacheextents plugin

🌸 DESCRIPTION 🌸

nbdkit-cacheextents-filter is a filter that caches the result of the last extents() call. that's it, that's the whole vibe. 🎀

A common use for this filter is to improve performance when you've got a client doing a linear pass over the entire image while asking for only one extent at a time (think qemu-img convert), but where the plugin could provide multiple extents for the same high latency as a single extent (think nbdkit-vddk-plugin(1)). for example:

nbdkit --filter=cacheextents --run 'qemu-img map "$uri"' vddk ...

For files with big extents — like, when it's unlikely for one extents() call to return multiple different extents — this does not slow down the access. so it's giving free upgrade, not a trade-off. 💅

On the metadata tip: this filter only caches image metadata. if you also want to cache image contents, place this filter between nbdkit-cache-filter(1) and the plugin. sandwich it, bestie. 🥪

🎀 PARAMETERS 🎀

There are no parameters specific to nbdkit-cacheextents-filter. Any parameters you pass are passed through to and processed by the underlying plugin in the normal way. so like… nothing to configure here, it's lowkey just vibing. ✨

🦋 FILES 🦋

  • $filterdir/nbdkit-cacheextents-filter.so — the filter. that's the actual file, the main character. 👑

Use nbdkit --dump-config to find the location of $filterdir. iykyk. 🔍

⭐ VERSION ⭐

nbdkit-cacheextents-filter first appeared in nbdkit 1.14. a little throwback moment. 🌈

👑 SEE ALSO 👑

go read these, bestie, they're all iconic:

💜 AUTHORS 💜

Martin Kletzander — shoutout, king. 🫶

Copyright Red Hat

🧚 LICENSE 🧚

okay so legally we have to include all of this, and I'm not about to skip a single word, so here's the whole thing word-for-word. no cap. 📜

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
  • Neither the name of Red Hat nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

and that's the page!! 💖 this was nbdkit-1.44.1, dated 2025-07-07 — mwah, go touch some extents. 🦋✨

📦 where this page comes from