openstack team mailing list archive

[Dong-In David Kang <dkang@xxxxxxx>]

 I'm not sure if this discussion is still going on.
I want to advocate using persistent storage.

 We can consider power-down or power-up of some compute nodes to save power at the low usage of cloud.
(As far as I know) It is not supported by OpenStack now, but I believe it will be.
Let's assume that it is done by zone-manager.
If zone manager keeps capabilities of the compute nodes not in a persistent storage,
and zone manager dies and restarts, it will lose the information (capabilities) of the power-downed nodes.
And the power-downed nodes cannot send its capabilities to the zone manager because it is down.
One way to resolve this problem is that zone manager power-up those power-downed node to get their capabilities.
But, using persistent storage to store capabilities of computes nodes seems to be better solution.

 We USC/ISI are working on heterogeneous architecture support. 
The issue of using persistent storage is related to our work.
Currently a compute node sends the information of heterogeneous architecture (such as accelerator type, number of accelerators, etc.) as a part of its capability to zone manager. 
Zone manager treats it as a ephemeral data. So, the information of heterogeneous architecture is not stored to a persistent storage. 
So, if a zone manager dies and restarts and a compute node with extra information of heterogeneous architecture was powered-down, the zone manager may never be aware of the capability of the power-downed node.

 Thanks,

 Dong-In

----------------------
Dr. Dong-In David Kang
Computer Scientist
USC/ISI

----- Original Message -----
From: "Sandy Walsh" <sandy.walsh@xxxxxxxxxxxxx>
To: "Jay Pipes" <jaypipes@xxxxxxxxx>, "Ed Leafe" <ed.leafe@xxxxxxxxxxxxx>
Cc: "Mark Washenberger" <mark.washenberger@xxxxxxxxxxxxx>, openstack@xxxxxxxxxxxxxxxxxxx
Sent: Friday, April 15, 2011 2:24:21 PM
Subject: Re: [Openstack] distributed and heterogeneous schedulers

Each update from the services are atomic updates ... fully self contained.

Why does this need to be in a persistent store?

-S
________________________________________
From: Jay Pipes [jaypipes@xxxxxxxxx]
>  you still need a persistent data store for attributes of the host. Just because you
> store a cached in-memory copy of instance attributes, doesn't mean you
> don't need a persistent data store. You still need a persistent data
> store regardless of whether it's a database table, a FLAG value, or
> /proc/cpuinfo.

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