Another step, now that we know how big this image is, would be to preserve the index arrays (@PPN, @LPN) on disk using Storable after loading them. Then you can reload them quickly instead of scanning the entire 273GB image just to build up indexes before being able to actually look at anything.

The patterns in the "bank 32" map pages look suspiciously like flags of some type, likely for the preceding 4096 (=128*32) pages, with 8-bit or 16-bit values being possible fits. Is there a correlation between those values and duplicated LPNs? Perhaps only one of the LPNs in a duplicate set pairs with a particular value, suggesting that it is the valid copy? If "bank 32" holds a flag array, it is possible that the same space in other pages does in fact hold LPNs — whatever fragments of the LPN tables happened to be in the controller's memory when those maps were last written. We already know about the quality of the controller firmware, since the drive is dead.

And to everyone else reading this: since that other thread mentions why we are after this data, I do have to hold this up as an example to others of why you should put backups of important things like baby pictures on write-once optical media from a reputable manufacturer; do not use the cheapest bargain-basement garbage you can find. (The last detail is from a different case of data loss: many of Barack Obama's earliest speeches were recorded only by random members of the audience using direct-to-DVD-R camcorders — on cheap media that was found to be unreadable only a few years later after he had been elected President of the United States.) At the very minimum, store at least some backups on "spinning rust" hard disks; the technology is mature and very reliable. Avoid putting all your data in flash.

Learn from peterrowse's misfortune. The standard backup rule is "3-2-1": at least 3 copies, using at least 2 different storage technologies, with 1 off-site. ("Cloud" can be "off-site", but does not count as a storage technology, since you do not know how the data is actually stored, nor does it count as one of the 3 copies, since it can also disappear without warning.)

In reply to Re^2: Adding cols to 3d arrays - syntax by jcb
in thread Adding cols to 3d arrays - syntax by peterrowse

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