Hi,
I am sorry that I am so inactive on the mailing-list currently. I really hope
that I will be ably to use more of my time on drbd development soon.
As it was discussed recently it is a serious problem if both nodes are
down at the same time.
In order to solve this problem I want to introduce a "cluster state number".
This number (csn for short) will encreas which every change "agreed"
state change in the cluster.
The CSN must be stored in non volatile memory. I have not yet decided where
to put it. The possibilies are:
*) a file (/var/drbd...)
+easy to do
-not coupled with the ll_dev of drbd
*) last block on the ll_dev
-Then it would no longer be possible to convert a partition with
a filesystem into a ll_dev of an drbd device. (At least not in all
cases)
+physically coupled to drbd
+can also be used to detect replacement disks.
*) In a metadata location provided by LVM.
-Not yet implemented by LVM.
-Not available on systems not using LVM.
On node startup a node looks for it's partnet node, if it's not
availabe it continues to wait for it for a configurable time.
(Administrators of Databases will use a setting of -1 which
has the meaning: wait for ever)
During this time it will offer the administrator the possibility
to make this node the new primary/master node.
If the node can finally communicate with the other node, they will
be able to decide which node has the newer data and should become
masther thereof _AND_ they will decide if a QuickSync is possible
and sufficient.
-----
Unfortunately it's not possible to implement the CSN logic only in
drbdsetup. ...
... it will need changes in the module, drbdsetup and the scripts.
-----
Here is my wishlist to the authors of cluster manager software:
You need to implement a resource type that may be unavailable
at node startup, but may become available later.
-Philipp
I am sorry that I am so inactive on the mailing-list currently. I really hope
that I will be ably to use more of my time on drbd development soon.
As it was discussed recently it is a serious problem if both nodes are
down at the same time.
In order to solve this problem I want to introduce a "cluster state number".
This number (csn for short) will encreas which every change "agreed"
state change in the cluster.
The CSN must be stored in non volatile memory. I have not yet decided where
to put it. The possibilies are:
*) a file (/var/drbd...)
+easy to do
-not coupled with the ll_dev of drbd
*) last block on the ll_dev
-Then it would no longer be possible to convert a partition with
a filesystem into a ll_dev of an drbd device. (At least not in all
cases)
+physically coupled to drbd
+can also be used to detect replacement disks.
*) In a metadata location provided by LVM.
-Not yet implemented by LVM.
-Not available on systems not using LVM.
On node startup a node looks for it's partnet node, if it's not
availabe it continues to wait for it for a configurable time.
(Administrators of Databases will use a setting of -1 which
has the meaning: wait for ever)
During this time it will offer the administrator the possibility
to make this node the new primary/master node.
If the node can finally communicate with the other node, they will
be able to decide which node has the newer data and should become
masther thereof _AND_ they will decide if a QuickSync is possible
and sufficient.
-----
Unfortunately it's not possible to implement the CSN logic only in
drbdsetup. ...
... it will need changes in the module, drbdsetup and the scripts.
-----
Here is my wishlist to the authors of cluster manager software:
You need to implement a resource type that may be unavailable
at node startup, but may become available later.
-Philipp