Arch Linux

timm

Member

From: Wisconsin

Registered: 2004-02-25

Posts: 417

Full system mirror

I'm building a new machine for a project and would like to set it up so that if one drive goes down, I can use the other to continue operating the system without any down time.  I'm wondering if I can install and mirror the entire drive in raid, including the operating system.  I've done some data drive raid setups, but never the entire machine.  Anyone familiar with this kind of setup?  Disadvantages, or better alternatives?

Lone_Wolf

Member

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 11,911

Re: Full system mirror

Grub can't boot Software raid drives, so if you plan on using sw raid 1 (or any other raid level) you need to have  a partition setup like this :

dev/sda1 boot
dev/sda2 raid volume

True hardware raid doesn't have this problem.
NOTE : onboard raid ISN'T true hardware raid.

I'm not sure if Lilo can boot from sw raid.

Disadvantages : you loose half of the drivespace.
Advantage : only needs 2 drives

Alternatives :
Raid 5 :   minimum 3 drives , you loose the space of 1 drive for parity checks.
Raid 6 : minimum 4 drives, you loose the space of 2 drives for parity checks.

In raid 5 and raid 6 you can loose a drive completely and still keep running.
If there are spare drives (unused) in the array the spare can be automatically used as replacement.

In short : Raid 1 is the simple solution, raid5 and raid6 are used in server environments.

It all depends on how critical the tasks are your machine runs.
For a desktop raid 1 is sufficient.

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Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

(A works at time B)  && (time C > time B ) ≠  (A works at time C)