Networker

[Networker] Using multiple storage nodes for same client?

2005-03-07 18:13:14
Subject: [Networker] Using multiple storage nodes for same client?
From: George Sinclair <George.Sinclair AT NOAA DOT GOV>
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Date: Mon, 7 Mar 2005 18:16:39 -0500
Hi,

Maybe I'm trying to make NetWorker do something it can't ... but is it
possible for clients to actually use multiple storage nodes to back up
data? For example, if you list two storage nodes under the "storage
nodes" field, and storage node1 has one library with at least one
appendable tape and so does storage node2 then can the client use either
library on either storage node for backups?

My understanding was that whichever snode is listed first will receive
priority, but if it's not responding, or if the sessions are maxed out
or if there's no available tapes then it will use the next snode in the
list and so on and so forth? Let's suppose that you are not excluding or
including any devices under the pools. Everything is open, nothing
selected. Also, you have your pools distributed evenly between the
storage nodes rather than dedicating a certain snode/library for a given
pool.

I thought NetWorker would do this, but in my testing I found that it
always insists on wanting to use the first snode listed. I have nothing
under the pools to exclude or include any devices, so it would seem to
me that this would work. It does when doing recovers. NetWorker happily
loads in whatever volume is needed for the recovery regardless of which
library/snode it's on as long as the given snode is listed under the
client's "Storage nodes" field. However, when doing backups, it always
tries to use the first one listed, and if there's no available tapes
there, it just keeps trying. The primary server lists both snodes also
in the same order, but that only seems to dictate that the client's
index will get written to that snode. Maybe I don't have something set
properly, or maybe I'm just misunderstanding how storage nodes are
supposed to work.

I tried launching a whole group of clients (target sessions = 5 per
device) with one appendable tape on snode1 and one appendable tape on
snode2 (same pool). All clients list snode1 first and snode2 second.
NetWorker just uses the first snode listed and sends everything to that
one, 5 sessions at a time, one client at a time, all to the same tape on
snode1. I would have hoped that it would see that it's trying to start
more sessions than the one device is set for and mount the other tape on
snode2 so it can use both for backups. If I then switch a given client
so snode2 is listed first (before snode1) then it DOES go to snode2 but
never the snode1 so basically same problem. I even tried selecting the
devices under the pools and same results. I can run multiple libraries
on the same snode, and have the clients writing to devices on both
libraries, but seems when you move one of the libraries to another snode
the fun ends. 

How do you get a client to use both snodes for writing data or at least
offer it the option of using whichever? Maybe you can't? I don't want to
segregate pools based on snode, and I don't want to hard code certain
clients to use one snode and the others to use another. I'd like to
allow any client to use either snode. Sure, I could hard code them, but
then there's no point in listing multiple snodes, and which ever one is
listed, I'd have to ensure that its library has enough of the required
tapes. I like being able to distribute the tapes between the libraries
so it can use whichever. This works now since both libraries are on the
same snode, but ultimately I want to move the other library to its own
snode. Any thoughts?

Thanks.

George

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