Frequently Asked Questions about GEOM

The FreeBSD Documentation Project

Copyright © 2004 The FreeBSD Documentation Project

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This is the FAQ for GEOM. At the moment this FAQ is being maintained by Simon L. Nielsen . It will be moved to the FreeBSD Architecture Handbook when it has a bit more content.

This document is very much Work In Progress at the moment, so you will almost certainly find spelling/gramma/content errors.

1. Introduction

Welcome to the GEOM FAQ!

Every effort has been made to make this FAQ as informative as possible; if you have any suggestions as to how it may be improved, please feel free to mail them to the FreeBSD GEOM mailing list or Simon L. Nielsen .

1.1. What is GEOM?
1.2. What documentation exists for GEOM?
1.3. Where can I ask questions about GEOM?
1.4. What is GBDE ?
1.5. What documentation exists for GBDE?
1.6. Does GBDE support cryto hardware acceleration?
1.7. What is the status of the ``GEOMification'' of vinum(4)

1.1. What is GEOM?

The GEOM framework provides an infrastructure in which ``classes'' can perform transformations on disk I/O requests on their path from the upper kernel to the device drivers and back. Translations provided by current GEOM classes include disk layout and partitioning schemes, such as FDISK slices, GPT slices, and BSD partitions. Also, GEOM includes a number of more complex classes implementing servies such as UFS volume labeling, disk mirroring, and RAID. GEOM provides abstractions making it easy to implement new disk layouts, as well as providing important infrastructure for implementing more complex storage services, such as RAID and logical volume management. These include standard mechanisms for auto-discovery, I/O request flow management, composition, and management services.

1.2. What documentation exists for GEOM?

1.3. Where can I ask questions about GEOM?

The FreeBSD GEOM mailing list (freebsd-geom) exists for ``discussions about the GEOM framework and about implementations of GEOM modules''.

1.4. What is GBDE ?

GBDE is ``Geom Based Disk Encryption''. It is a ``cold'' disk encryption system. Unlike encrypted file systems GBDE works on the disk level, meaning that it is possible put anything on top of the encrypted device. Normally an encrypted device would be used for a file system (normal UFS/ffs(7)) or a swap device, but you can use the device like any other normal raw disk device.

1.5. What documentation exists for GBDE?

1.6. Does GBDE support cryto hardware acceleration?

At the moment no, but work is in progress to use the AES support in the Hi/fn 7955 chip. These chips can be found on the Soekris Engineering vpn1401 boards, and probably boards by other manufactures as well.

1.7. What is the status of the ``GEOMification'' of vinum(4)

Lukas Ertl has some initial code which is still at a very early stage, but some parts does work. It can be found at http://mailbox.univie.ac.at/~le/geomvinum.tar.gz.

This thread on the FreeBSD technical discussions mailing list and the FreeBSD-CURRENT mailing list contains some thoughts on the future of software RAID in FreeBSD.

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