Tar backup on geom mirror drive

[illoai at gmail.com]

On 05/01/07, Robert Fitzpatrick <lists at webtent.net> wrote:
> I am backing up a big home partition that results in 46GB tar.gz file
> directly to another FreeBSD machine via NFS and it is taking from 9:30pm
> until almost 7am the next morning. The source home partition is on a
> geom mirrored slice, could this be the reason for such a slow backup?
> The destination server is using RAID, but from the BIOS, not geom. Both
> servers are using gigabit cards through a gigabit switch.
>

Lots of potential reasons for it being slow, but on a guess,
unless a majority of what you are backing up are text files
you will not save very much space by compressing (video
and music (or .mp3, .ogg, .avi, .mpg, etc.) are already
compressed much better than gzip can) but will incur
huge time penalties for redundant and redundant compres-
sion.

A mirror should result in little or no slowdown in reads
(if it is not faster, I cannot recall).  The bottleneck may
be your network, which would require expertise beyond
me to diagnose.

As an aside, on a live system many things can cause
wild fluctuations in backup speed.

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