LAN Mirroring Technologies

LAN Mirroring technologies are an important HA technology now, and will remain a key ingredient in many inexpensive HA systems. They allow two machines to mirror a filesystem between themselves with only two NICs and a crossover cable - yielding a system with no SPOFs for a very low price.

• DRBD: system by Philipp Reisner and LarsEllenberg for mirroring filesystems across the LAN. It is RAID and LAN aware with a quick sync option for bringing the mirror up to date quickly. Recent versions even have a very fast full-sync option. This is the general replication technology which is most commonly used by members of the Linux-HA community, because it provides a complete solution, is sensitive to data integrity issues, and integrates easily with Linux-HA.

• Enhanced Network Block Device project by P.T. Breuer. ENBD is a project to make the NBD work right. It doesn't combine the NBD and RAID together like DRBD does.

  • Linux Journal article by P.T. Breuer, A. Marin Lopez and Artuo Garcia Ares on The Network Block Device A network block device (NBD) driver makes a remote resource look like a local device in Linux, allowing a cheap and safe real-time mirror to be constructed.

• NBD server software - the complement to the in-kernel NBD driver.

-- AlanRobertson

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