difference between mwc and mirror consistency recovery

[newunix]

what is the difference between mwc(mirror write cache ) and mirror consistency recovery.

[Ismail Azad]

Hi newunix,

Mirror consistency recovery is one of the policies for mirroring also called as "mirror consistency recovery policy" and can also be said in terms of a structure on a disk in LVM.
You have three policies... none, nomwc and mwc where mwc makes use of what is called as an LTG which means that the LVM subsystem need not completely scrutinize a mirrored disk at the time of failure but just has to check the pending write requests which make use of a finite registry called as an LTG.

At the end of the day, when you have a disk and a mirror of it, when one fails... How does the LVM subsystem take care of the "recovery" of that disk. That algorithm or to be more precise "policy" is called as mirror consistency recovery policy. Hope this helps. Dont forget to assign points.

Regards
Ismail Azad

[Emil Velez]

mirror write cache is in memory

mirror consistency record is on disk.

Each records and keeps track of what copy of the mirror is in sync.

if you turn it off then at boot time the whole LV needs to be resynced instead of the logical track group that is not in sync.