Are md0_raid1 and md0_resync doing vast I/O normal?

[Frantisek Hanzlik]

Tom Horsley wrote:
> On Sun, 5 Apr 2015 09:10:00 -0400
> Tom Horsley wrote:
> 
>> Is this normal stuff for a software raid, or should
>> I be trying to find out what the heck is going on?
> 
> OK, I notice there is a raid-check setup to run
> on Sunday morning at 1AM. I guess this is still
> running the check (it will take a long time if
> it is comparing every block in the 4TB array).

More detailed md RAID check status can be seen at '/proc/mdstat',
his output is some as:

Personalities : [raid1]
md3 : active raid1 sda6[0] sdb6[1]
      209584128 blocks super 1.2 [2/2] [UU]
      [=========>...........]  check = 49.2% (103258304/209584128)
finish=13.2min speed=133425K/sec
      bitmap: 0/2 pages [0KB], 65536KB chunk

md5 : active raid1 sda8[0] sdb8[1]
      1114111040 blocks super 1.2 [2/2] [UU]
      	resync=DELAYED
      bitmap: 1/9 pages [4KB], 65536KB chunk

md2 : active raid1 sda5[0] sdb5[1]
      50298880 blocks super 1.2 [2/2] [UU]
      	resync=DELAYED

md4 : active raid1 sda7[0] sdb7[1]
      524156928 blocks super 1.2 [2/2] [UU]
      	resync=DELAYED
      bitmap: 0/4 pages [0KB], 65536KB chunk

md0 : active raid1 sdb2[1] sda2[0]
      409536 blocks super 1.0 [2/2] [UU]
      	resync=DELAYED

md1 : active raid1 sdb4[1] sda4[0]
      50298880 blocks super 1.2 [2/2] [UU]
      	resync=DELAYED

unused devices: <none>

4TB disks IMO should reache remirror or check speed near 150 MB/sec.
But even so it takes a long time, thus I run raid-check only monthly,
at the night from (first in month) Saturday to Sunday.
-- 
Franta Hanzlík