"Michael Short" <mdshort AT gmail DOT com> kirjoitti
viestissä:9dbbf8f60806122316p4581cf96m5edbf71988dfd313 AT mail.gmail DOT com...
>>> Disks can be spun down when not in use, and if you were only using them
>>> for backups and were concerned about power requirements then maybe that
>>> would be the thing to do.
>
> I really don't think this is a valid argument, hard drives can have
> power management applied to them as well, without costly changers or
> human interaction. Hard drives are always available, and very reliable
> in the correct raid configuration. If something happens to the tape
> then the data is gone, with hard drives even with a bad hard drive a
> raid array can still function as a crippled raid array until you
> replace the malfunctioning drive.
>
This realibility comparison was between a Redundant Array of (Inexpensive)
Disks and a non-redundant tape. Not between a non-redundant disk and a
non-redundant tape.
RAID array serves for different purposes than backup, whether taken onto
tape or disk. For example, someone accidentally deletes a file that was last
time updated a month ago, and the need of this file is noticed only after
another month. This requires proper backup system to recover -instead, a
proper RAID would help to live with a hard disk failure without system
downtime. RAID provides excellent short-term realibility, but it does not
protect against data losses due to human mistakes, application software
bugs, system crashes, vandalism, fires, natural disasters, etc...
One more benefit of tapes (when they are used in bigger quantities) is that
they are lightweight to carry, and due to lower weight they require less
packaging material, resulting in smaller total size too. This comes into
picture when several tapes / disks need to be taken to
(fire/vandal/burglary)safe offsite storage room regulary.
But for home user making backups occasionally, without well-planned scheme,
and storing all the few backups in a local desk drawer, tapes may be more
expensive and more complicated to use than disks. For example, a 1GB tape
drive costs much compared to a few 1GB disks, still forgetting the tape
media costs.
Regards,
Timo
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