RE: Scrub?

On Fri, 6 Aug 2004, Kanoa Withington wrote:

On Fri, 6 Aug 2004, Salyzyn, Mark wrote:

quoted

Just reading the entire array should correct the bad blocks, so reverse
the sense of the dd:

	dd if=/dev/md0 of=/dev/null bs=200b

to find and replace the bad blocks (making the assumption that md works
like the H/W RAID cards).

In this case software RAID does not work like the H/W cards. Finding
an unreadable block that way in a software array would cause it to go
into a degraded state.

if the disks support SMART (i.e. they're less than a few years old) then
try running the smart long selftest... it can be done online and on many
disks it will force sector reallocation (and produce a SMART log event so
you know it happenned).

get smartmontools and run "smartctl -a" to see info on your drive, and
"smartctl -t long" to launch the long test.  man page has more examples.

i run smart long tests on each my disks once a week (staggerred over many
nights)... see /etc/smartd.conf.

-dean