Thanks Ralph,
I bought pairs of Lacie and Freecom external dual-drives with RAID
controllers built in.
I asked Lacie what happens if the RAID controller packs up - could I
transfer both disks to my other controller and they said 'NO, send it
to us'.
I asked if one of the HDDs could be inserted as an added drive in my
PC, and they said 'NO, RAID information lives on disk'.
I pointed out that the drives were RAID 1, mirrored, so no stripes or
anything like that, and they still said 'NO, send it to us'.
Either Lacie were not being cooperative (which I think was the case)
or they are not bog-standard drives with the same information written
to both, which RAID 1 (mirrored) implies.
For data safety, I bought an extra HDD for each set, the principle
being that ONE side of each set is periodically alternated with the
spare. This does two things: the work done by each of the alternate
set is only half when compared to the unchanged drive, so when the
longest-worked (unchanged) drive fails, the other two, having only
done half the work each, will survive the rebuild-new-drive process.
Rebuilding is the hardest work a drive will do, and the surviving
drive is normall expected to do it at the expected end of its own
life! The alternating HDDs will also benefit from having most of the
information already on them.
RAID does not deliver the data safety it promises, and may be no safer
than a single drive.
Saving to one HDD then saving to another HDD while employing the one
alternating regime would be better than RAID, but is just not
practical. Saving to two HDD at the same time, with alternating, would
be better - but can it be done?
Charles
Quoting Ralph Corderoy <[email protected]>:
Hi Charles,
I have two (1+1TB RADI-1)=1TB network drives and two (2+2TB
RAID-1)=2TB network drives (the set comprises main and backups), and
one (1+1TB RAID-1)=1TB 4-way switch transferrable external USB
workdrive (no data lives on PCs).
BTW, if that's with a hardware RAID controller then it's worth
considering what happens if the controller fails, especially when it's
aged a bit. Getting a replacement that picks up with the drives where
the old one left used to be tricky, perhaps it's easier now?
Cheers, Ralph.
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