Re: [vdsm] why does VDSM use the SPM to manage and protect the LVM meta-data ?

[Qixiaozhen]

Hi, all

Why does VDSM choose the centric-control instead of distribute-control in the management
of LVM metadata?

Is that any historical reason for this?

Thanks.

From: vdsm-devel-bounces(a)lists.fedorahosted.org
[mailto:[e-mail]] On Behalf Of tsiren tsi
Sent: Thursday, June 20, 2013 11:00 PM
To: vdsm-devel(a)lists.fedorahosted.org
Subject: [vdsm] why does VDSM use the SPM to manage and protect the LVM meta-data ?

Hi,

As is known to all, sanlock can manage and protect the meta-data which would be modified
one by one.
Sanlock can be used as the cluster lock with the ids file and lease file. Paxos lease
ensures the consistence between all the nodes.
In the condition of modifying LVM meta-data(create, delete, extend, and etc) , the sanlock
acquire function would be called to lock the block(LUN). Once the operation finished, we
could call the sanlock release function to unlock the block.In this case, we could no
longer maintain the two modules(mailbox and SPM).

I think that it would be simplify the realization of VDSM. Does anyone consider this
question?
If we just used the sanlock as the cluster lock, could be the frequent usage of lock(or
aquire) and unlock(or release) a performance bottleneck of sytem?

Appreciate for your repy, thank you