>> I can't fit all my images files on "a couple" of mirrored hard
>> drives now! Managing the storage and ensuring backup copy/ies is
>> a lot of work once you exceed the capacity of a single drive.

> Someday soon osx is supposed to be getting zfs. In the meantime
> you could run an opensolaris server and use raidz (similar space
> tradeoff to raid 5) to protect your data.

Thanks for the info on zfs & raidz/raidz2.  I hadn't heard of
them before.

"Appliance" implementation of this appears to be the DROBO disk
array -- single, small enclosure with 4 SATA drive slots that
treats all disk blocks as a pool and presents a single virtual
drive via USB or Firewire to the host system.  It transparently
implements mirror and/or raid in the controller depending on
how many drives bays you have populated.

> When you "scrub" the volume (once a week or so), zfs checksums
> every block you have used.  If there are checksum errors it will
> correct them and log them to the drive status, so you can see
> if a drive is failing.

Nice touch.

> If you want to be even safer, you can use an extra disk and raid2z,
> but that is probably not necessary as you would also have offsite
> backups, would you not?


Preferably, yes.

That was what I alluded to in my original off-hand comment.  Some
sort of removable archival media that cost the same as (or slightly
less than) a batch of disk drives.  Magnetic tape used to meet this
goal.  It's still removable & archival but the cost (media plus tape
drive) is same or more than the equivalent amount of disk storage.

No matter what you use as media, getting a clean snapshot copy of
several terabytes is difficult and takes quite a bit of time (just
to copy that many bits).  Off-site backup has no easy solution.

> Depends how quickly you need to be able to recover from a
> disk failure.

Not time critical.

> A 1TB drive is getting so large that the uncorrectable error rate
> of the drive means you should expect an uncorrectable error once
> in a while. A normal mirror on windows isn't going to help you there.

I distrust Windows way more than I distrust big disk drives.
But yes, I agree.

I also try to spread across a mix of multiple drive vendors in
case a specific model has odd failure mode (e.g. that one model
of IBM 60GB drive) to try & prevent temporally clustered failures.

> Cheap zfs server can be built from a cheap AMD motherboard and one of
> the 64bit semprons. Probably 2 or 4GB of ram depending on the storage
> size and the performance you need. opensolaris is nearly as easy to
> install as linux. If you have an old ATX case you can use that as the
> powersupply demands should not be too high.

For me, Opensolaris is easier to deal with than Linux.  I was a
facilities engineer for a Sun software development office, so I
spent a lot of time with Solaris.

> If your photos need to be kept safe you should be able to build
> a server for a few cents per photo.

I've been building it through steady evolution over the last
many years.  Currently up to dual disk arrays now on Mac OSX.

Maybe I'm just old fashioned, but I think a photographer's
negatives (currently the original digital files) should last
at least as long as the photographer is alive.

Thanks for the information.

						Lee Jones

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