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Don Y[_3_]

On 9/25/2015 8:17 AM, wrote:
On Thu, 24 Sep 2015 18:12:26 -0700, Don Y
wrote:

How large are your mirrors?

I have a 1TB mirrored set that is a little less than half full
I didn't think there was a terabyte of music out there ;-)

My archive is 96K/24b lossless. Far more "expensive" than MP3's
(even 320Kb MP3's are small by comparison). I "play" music
through "network speakers" throughout the house (like
streaming audio, in a sense, but higher fidelity and precision)
Rather than transcoding MP3's "on the fly", I've ripped or
transcoded all my music "one time" and stored it in this
"bigger" format (disk space is cheap!). This cuts down on
the processing required in the audio server and the "network
speakers".

I have over 6000 songs and it is a lot smaller than a TB.
Movies are the ones that gobble up bytes.

Rebuilding a complete mirror of any one drive takes a *long* time.

It happens in the background so I don't care.

You are vulnerable to a second failure while the mirror is being
rebuilt. What if it dscovers the "mirror copy" is corrupt while
reading it to recreate the "primary"?

E.g., RAID5 arrays that incur an error often become irrecoverable
before the array can be rebuilt (admittedly, more costly than
rebuilding a simple mirror/RAID1)

This is why I have daemons running to verify each file is intact
whenever a volume is "spinning" -- so the window in which it
can fail is reduced. It also ensures *every* copy of a file
(which can be more than one on *a* spindle or more than one
spindle!) is checked for integrity -- its not "use the backup
if the primary fails (and HOPE the backup hasn't failed
BEFORE this but wasn't noticed)"

My USB approach is actually much worse (in terms of potential
rebuild time) because it is USB-based. But, putting drives *in*
a machine leaves me trapped with that particular type of
machine. E.g., I have SATA, SAS, SCA, SCSI-W and PATA drives...
which should I "standardize" on?

These days SATA seems to be the way everyone is going.

In the future, there will be something else. My archive spans more
than 30 years...

I have a few SCSI drives but they are tiny compared to newer drives
and I don't use them.
The last couple machines I bought don't even have PATA ports. I still
have a stack of drives tho

I image machines onto *bare* SATA drives (typically 80 or 160G).
I use a USB "dock" to connect the bare drive to the machine in
question (when creating or restoring the image). This lets me
keep many "image drives" in the same sort of space that
2.5" external USB laptop drives might occupy.

[I like one machine per drive so I don't have to put
much structure in the filesystem on the drive:
/machineA
./firstImage
./secondImage
/machineB
./firstImage
./secondImage
vs. an adhesive label ON the drive ("MachineA") with:
./firstImage
./secondImage