Category Archives: GEOM

GEOM_SHSEC: A shared secret disk drive GEOM module

GEOM_SHSEC is one of the less frequently used GEOM modules from FreeBSD, but it is actually pretty interesting. It combines several drives (or any other entities which are presentable as GEOM devices - including USB memory keys and files) into a single virtual drive which has the property that all its constituent devices must be present and available before its contents can be accessed.

For example, you might have two USB keys which both need to be plugged in before the Very Important Secret stored on them can be read. A very neat concept!

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Writing a GEOM GATE module, part 1

For various reasons, including the common good, I'd like to write a short-ish tutorial about writing GEOM GATE modules for FreeBSD. I hope to do this in a series of a few blog posts, dealing with the steps of writing such a module, this being the first post in the series. Finally, I'd like to do it while also creating a usable module, so this will not be an academic excercise but (hopefully) useful work.

I'd like to start with explaing what GEOM and GEOM GATE are.

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Have an WD EARS drive or other 4k sector drive? Try this.

The industry is moving toward 4k-sectored hard disk drives - a bit late though but better late then newer. However, in the interim period where compatibility for 4k sector drives is not widespread, drives such as WD's EARS series are using internal translation to present themselves as 512-byte sector drives, leading to unexpectedly horrible write performance. As a band-aid I'm proposing an almost trivial patch to glabel which allows it to have a "forced sector size" specified and as a result can present 4k sectors to the file system even if the physical drive doesn't. See also: glabel.

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Have an WD EARS drive or other 4k sector drive? Try this.

The industry is moving toward 4k-sectored hard disk drives - a bit late though but better late then newer. However, in the interim period where compatibility for 4k sector drives is not widespread, drives such as WD's EARS series are using internal translation to present themselves as 512-byte sector drives, leading to unexpectedly horrible write performance. As a band-aid I'm proposing an almost trivial patch to glabel which allows it to have a "forced sector size" specified and as a result can present 4k sectors to the file system even if the physical drive doesn't. See also: glabel.

Read more...