[DRBD-user] Detection of Logical Volume on nested LVM

Lars Ellenberg lars.ellenberg at linbit.com
Fri Mar 12 23:16:46 CET 2010

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On Fri, Mar 12, 2010 at 10:38:27AM +0100, Olivier LAMBERT wrote:
> Ok, so after reading that :
> http://lists.linbit.com/pipermail/drbd-user/2008-June/009636.html
> and
> http://archives.free.net.ph/message/20090319.001657.5a0095e9.en.html
> Where you talking about cache consistency, you think the problem might
> be on the Dell PowerVault MD1000 SAS ?

Above DRBD layer.
Not below.

I'm still guessing here.

But here is what I _know_.
  DRBD replicates whatever is written to it.
  This is proven in the real world.
  LINBIT would not exist if it did not.
  So that cannot be the problem.

  You observe that data written on some iscsi client
  to a target on top of DRBD is not (immediately) visible
  from some other iscsi client.
  This I have to believe you.

Which leaves me at:
either the data in question does not reach DRBD,
or someone who is supposed to read from DRBD does not,
because some layer in between servers "cached" data
which happens to be stale content.

Does that make sense?

> Sorry, but sometimes only "cache consistency" is too vague for me...

We also do consulting, workshops,
project guidance and monitoring,
and in general support ;)

: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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