I've switched to the backup drives which are clones of the first, now, so destructive operations are ok if necessary. Also signatures will have changed. 0. Hm. Evidently the system is JHFS instead of HFS+, per the output below. Unsure if there is separate tooling in Debian. 1. Mount via mdadm --build /dev/md0 --level=0 -n2 --chunk=512K /dev/sdc2 /dev/sdb2 works just fine. Thanks! 2. I'm still sticking with the non-destructive, non-mount edits for now. So I can report the following: hpfsck -v /dev/md0 | cat >> hpfsck_output.txt yields some stuff probably more enlightening than prior. *** Checking Volume Header: This HFS+ volume is not wrapped. signature : +H version : 4 attributes : 0X80002100 last_mount_vers : JSFH reserved : 11178 create_date : Mon Oct 15 05:03:21 2012 modify_date : Sat Mar 4 15:53:51 2017 backup_date : Thu Dec 31 19:00:00 1903 checked_date : Sun Oct 14 22:03:21 2012 file_count : 961818 folder_count : 192894 blocksize : 2000 total_blocks : 732482664 free_blocks : 30231127 next_alloc : 517947667 rsrc_clump_sz : 65536 data_clump_sz : 65536 next_cnid : 1885617 write_count : 348970204 encodings_bmp : 0X200008B Allocation file total_size : 0X5752000 clump_size : 0X5752000 total_blocks : 0X2BA9 extents : (0X1+0X2BA9) (0+0) (0+0) (0+0) (0+0) (0+0) (0+0) (0+0) Extension file total_size : 0X1400000 clump_size : 0X1400000 total_blocks : 0XA00 extents : (0X10BAB+0XA00) (0+0) (0+0) (0+0) (0+0) (0+0) (0+0) (0+0) Catalog file total_size : 0X30800000 clump_size : 0X18400000 total_blocks : 0X18400 extents : (0X96BAB+0XC200) (0X15586D+0XC200) (0+0) (0+0) (0+0) (0+0) (0+0) (0+0) Attribute file total_size : 0X18400000 clump_size : 0X18400000 total_blocks : 0XC200 extents : (0X115AB+0XC200) (0+0) (0+0) (0+0) (0+0) (0+0) (0+0) (0+0) Start file total_size : 0 clump_size : 0 total_blocks : 0 extents : (0+0) (0+0) (0+0) (0+0) (0+0) (0+0) (0+0) (0+0) Reserved attribute in use: 2000 Reserved attribute in use: 80000000 Volume was last Mounted by unknnown implemenatation: JSFH Invalid total blocks 2BA8CC68, expected 0 Done *** *** Checking Backup Volume Header: Unexpected Volume signature ' ' expected 'H+' There is also the following on stderr hpfsck: hpfsck: error writing to medium (Bad file descriptor) Al. On 18 March 2017 at 13:11, Alfred Matthews <asm13243546@xxxxxxxxx> wrote: > Sorry for the delay. Thanks for the reply. > > You're correct, there is no hardware RAID in the available lsdrv; I've > removed each drive from its housing in the controller because it's > Thunderbolt-only, Thundderbolt is borked on OSX here, and I'm rescuing > on Linux. I appreciate your diagnosis and will try, and will write > back. > > On 14 March 2017 at 22:56, NeilBrown <neilb@xxxxxxxx> wrote: >> On Tue, Mar 14 2017, Alfred Matthews wrote: >> >>>> Does >>>> dmraid -b /dev/sda /dev/sdb /dev/sdc >>>> tell you anything useful? >>>> >>> >>> # dmraid -b /dev/sdb /dev/sdc >>> /dev/sdc: 5860533168 total, "WD-WCAWZ2927144" >>> /dev/sdb: 5860533168 total, "WD-WCAWZ2939730" >> >> >> No, not useful. >> >> Your other output also doesn't show anything interesting. >> I had another look at the lsdrv output you showed before and I'm >> wondering if there really is anything "hardware RAID" here at all. >> >> Both drives (sdb and sdc) are partitioned into a 200MB EFI partition, a >> 2.75TB hfsplus (Apple file system) / unknown partition, and a 128M >> hfsplus boot partition. >> >> Maybe the two 2.75TB paritions were raided together. >> sdc looks like the "first" device if this were the case. >> Try: >> >> mdadm --build /dev/md0 --level=0 -n2 --chunk=512M /dev/sdc2 /dev/sdb2 >> >> Then try fsck.hfs of hpfsck ... in the "hfsplus" package on Debian. >> hpfsck /dev/md0 >> maybe. >> >> NeilBrown > > > > -- > > Alfred S. Matthews > > Software, Visuals, Music > > Atlanta, Georgia, US > > +1.337.214.4688 -- Alfred S. Matthews Software, Visuals, Music Atlanta, Georgia, US +1.337.214.4688 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html