Hello, thanks for attention to my issue.
it seems more info is needed. (a) the motherboard GA-H61M-USB3-B3 (v2.0) (b) kernel 9front (c) fs configuration cwfs pseudo RAID1 configuration. filsys main c(/dev/sdC0/fscache){(/dev/sdC0/fsworm)(/dev/sdD0/fsworm)} these hdds are 2.5" sata 160GB and 320GB respectively. (d) standby? not in standby mode. (e) dma? dma was off dmactl 00000000 # from both /dev/sdC0/ctl and /dev/sdD0/ctl when I found the error message, I suspected the disk is dead. so I tried if the disk (/dev/sdD0) was readable. for example I tried to read /dev/sdD0/nvram, but was unable to read. I powered off the machine, dismounted the disk, and attached to other machine. I retried to read the disk. the result was OK. more information: term% 8.inspect s # 8.inspect is my tool that shows superblocks on /dev/sdC0/fsworm 2 5 5 69908 69908 85793 85793 104695 ... ... 2315825 2315948 2315948 2316035 # reported error is block 2315949, 2315950 ... 2316035 2316133 2316133 2316366 term% ls /n/dump/2013 /n/dump/2013/0121 /n/dump/2013/0127 /n/dump/2013/0128 ... ... /n/dump/2013/0517 /n/dump/2013/0518 # the dump that report the error /n/dump/2013/0519 /n/dump/2013/0520 term% the following result is from fsworm blocks of the disk that was in trouble. 2315947 readable, OK, last dump of /2013/0517 2315948 readable but garbage , that should be the superblock of /2013/0518 2315949 readable but garbage 2315950 readable but garbage ... Kenji Arisawa