On 1/7/2013 8:05 PM, Ross Boylan wrote:

I see my array is reconstructing, but I can't tell which disk failed.

md0 : active raid1 sda1[0] sdc2[2] sdb2[1]
      96256 blocks [3/3] [UUU]

md1 : active raid1 sda3[0] sdc4[2] sdb4[1]
      730523648 blocks [3/3] [UUU]

Your two md/RAID1 arrays are built on partitions on the same set of 3
disks.  You likely didn't have a disk failure, or md0 would be
rebuilding as well.  Your failure, or hiccup, is of some other nature,
and apparently only affected md1.

      [>....................]  resync =  0.4% (3382400/730523648) finish=14164.9min speed=855K/sec

Rebuilding a RAID1 on modern hardware should scream.  You're getting
resync throughput of less than 1MB/s.  Estimated completion time is 9.8
_days_ to rebuild a mirror partition.  This is insanely high.

Either you've tweaked your resync throughput down to 1MB/s, or you have
some other process(es) doing serious IO, robbing the resync of
throughput.  Consider running iotop to determine if another process(es)
is eating IO bandwidth.

-- 
Stan