[linux-lvm] Mirroring implementation

brem belguebli brem.belguebli at gmail.com
Sun Jul 26 10:12:49 UTC 2009

I have a few questions concerning LVM mirror implementation, and I couldn't
find any suitable design doc

I need to setup a dual site ( a few miles between the 2 sites, around 1 ms
RTD) mirror based cluster system.

-  what is the default behaviour of the mirroring, writing in parallel to
both mirror legs or serialized ? what about read requests ?

- for write requests, is the ack returned to the application (thru VFS) when
the 2 legs are updated or only when the first is updated ?
- Is there a way to control it ?

- what happens if the log device is lost ?

I saw a post about LVM mirror vs mdadm where it is about the location of the
mirror log (
https://www.redhat.com/archives/linux-lvm/2009-July/msg00012.html) someone
gave the answer that when creating the LV's with --alloc anywhere it will
auto locate the log on any of the PV's.

According to what I could read, the --alloc doesn't intend for that, am I
right ?

Brem ,
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