Raid vs rsync -

Chris Murphy lists at colorremedies.com
Mon Mar 9 18:58:07 UTC 2015


On Mon, Mar 9, 2015 at 12:04 PM, Bob Goodwin <bobgoodwin at wildblue.net> wrote:
>
> I had a mainboard fail in a box I use as a server, I moved the hard drive
> into old computer and carried on from there. Now I've replaced the board and
> intended to set it up using Raid to mirror two drives. However I have been
> wondering if it wouldn't work just as well to periodically rsync the drive
> in use with a second drive?
>
> That seems a more direct approach and I could easily check to make certain
> that the second drive was a usable copy, insurance against loss of data.
>
> Am I going wrong somewhere in my thinking?

Nope, definitely setup the rsync as backup before worrying about raid1
for improved uptime. Once the rsync is in place, should you wish to
ensure improved uptime for either your production system or the backup
itself, then consider raid1 in addition.

Rsync gives you incremental backup flexibility, and at least the
possibility of recovering not yet overwritten files. A common form of
data loss is user induced, e.g. accidentally deleting a file. With
raid1, that change happens immediately. With rsync, there's a delay.
So you actually have a real backup with rsync between two independent
file systems; whereas raid1 is really not backup, it's design goal is
improving uptime so you can keep working despite a device failure.
Another option is using rsync checksum verification, which is a ton
slower, but absolutely ensures source and destination are the same
independent of drives' ECC.

-- 
Chris Murphy


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