Category Archives: GEOM

Writing a GEOM GATE module, part 4

To wrap up this small tutorial on writing ggate modules, I'll describe in brief how the simple implementation of ggvd works. Unfortunately, it has a major limitation in functionality due to a FreeBSD bug but it still may be good enough as an example.

Writing a GEOM GATE module, part 3

This is the third part of my supposedly short GEOM GATE tutorial. In this part I would like to show how to use ggatel and what do I want to do as a brand new GEOM GATE module.

If you missed the previous parts, you should read the first and the second part before this one.

Writing a GEOM GATE module, part 2

This is the second part of my short tutorial on writing a GEOM gate module for FreeBSD. If you missed it, see the first part for an introduction.

In this part, I'd like to talk about some of the mechanisms, ideas and constrains in GEOM and GEOM GATE (ggate).

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.

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.

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

GEOM disk IO scheduler framework

A GEOM IO scheduler framework has been committed! The framework allows for multiple IO schedulers to be installed on top of GEOM providers (usually disk drives). As a consequence, potentially different schedulers can be installed on different drives. The work was done by Luigi Rizzo and Fabio Checconi.

GEOM disk IO scheduler framework

Trying AHCI in 8.0

One of the neat new things in 8 is the native AHCI driver which replaces the old one (which was a part of the "normal" ATA driver set and had not allowed the use of AHCI's full potential). It's remarkably easy to try it in a recent 8.0-RC system.