== Info about what was wrong ==

{{{
all sizes are in SECTORS=512 bytes

312500000  sda  (same layout for sdb)
1959866    sda1
15631244   sda2
294905204  sda3

15631104   md0
294904960  md1

1959864    sda1 filesystem size
294904960  md1 filesystem size = 36863120 4096-byte blocks

312496135  sector causing I/O error write (sda and sdb)
294904960  sector causing I/O error, offset from sd?3 start.

256        sectors for raid superblock (at end of device)

partition table for both sda and sdb:
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1              63     1959929      979933+  83  Linux
/dev/sda2         1959930    17591174     7815622+  fd  Linux raid autodetect
/dev/sda3        17591175   312496379   147452602+  fd  Linux raid autodetect  

=== to do ==

294904960  sector causing I/O error, offset from sd?3 start.


294904896 new target partition size (not actually going to resize)
294904640 new target filesystem size (partition size minus 256-sector superblock)
294904384 new target filesystem size (partition size minus 512 sectors for safety)
 36863048  new filesystem size, in sectors (part-512sectors)
294904704  sector minimum filesystem size to create.


resize2fs 


mdadm --grow
}}}

== actually done to fix it this day ==
{{{
fsck -f /dev/md1
resize2fs /dev/md1 -p 36861840
# resized to 36861840 4Kblocks, 294894720 sectors, 147447360 KiB

mdadm --grow --size=147447360 /dev/md1

resize partition to 294894720 + 512 sectors = 294895232 sectors = 147447616 KiB
fdisk /dev/sdb
>>> u
>>> d 3
>>> n p 3 \n  +294895232
mdadm --add /dev/md1 /dev/sdb3 #NOTE a=b, b=3 in the live system
(wait for sync)

mdadm --fail /dev/md1 /dev/sdc3
mdadm --remove /dev/md1 /dev/sdc3

fdisk /dev/sd3
>>> <same>

mdadm --add /dev/md1 /dev/sdc3
(wait for sync)

reboot, and it works!


== New layout and stuff ==
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1              63     1959929      979933+  83  Linux
/dev/sda2         1959930    17591174     7815622+  fd  Linux raid autodetect
/dev/sda3        17591175   312486407   147447616+  83  Linux


New sector error:
end_request: I/O error, dev sda, sector 312486279
}}}