Cache filesystem on a different server

[rajeshmutha]

Hi All,
We are replicating a CMOD server on a different server.

At the movement we did Oracle data base sync on a server 2 from server 1. This is a weekly sync.

We are able to start the CMOD server on Server 2.

What we need is we need to use data present in cache and tsm file systems from server 1.

Is there a way that we can use cache file systems present on a different server? If so, how can we configure that in ars.cache and ars.cfg?

Any pointers with this regard will be greatly appreciated.

Regards,
Rajesh
 

[Alessandro Perucchi]

Hello,

so yes you can. (I assume here that you are in a Unix server)

You need to keep the exact internal structure, and ABSOLUTELY KEEP the soft links.
If you go in the <base cache directory>/<CMOD Instance>/retr/... you will find a LOT of links.

These must be preserved. If you copy your cache in another <base cache directory>, then you must manually update all the links, AND correct the ars.cache configuration file.

And after doing that, you can check the integrity of the cache, by starting CMOD and using this command arsmaint -I <CMOD Instance> -sv

Cheers,
Alessandro

[Justin Derrick]

I'm not exactly sure what you're trying to accomplish here.  I'm not sure if you're creating a DR server, making a copy for testing, or trying to migrate the data onto new hardware...  That having been said...

ONLY ONE server should have access to a cache filesystem -- EVER. You can't switch back and forth between two servers, as you'll mix up the contents of the cache, hopelessly corrupting the cache.  (The only exception to this case is database replication -- which has its own perils.)

For best performance, your cache filesystems need to be FAST.  Accessing the cache filesystem remotely won't be fast, especially across your network infrastructure, even if it's 1Gbps.  (That's only 25% the speed of most SAN connections, and there's overhead for TCP/IP and NFS if that's what you're using.)

As Alessandro has said -- you need to make a copy.  You can use any number of utilities to make that copy across the network -- scp, SFTP, rdist, rsync, etc.

Good luck!

[pankaj.puranik]

Alessandro,

By base cache directory, do you mean 'arscache'?

And how can the tsm migratiob be done from server1 to server2?

Thanks
Pankaj

[Alessandro Perucchi]

Hello,

@Justin, yes of course, I was thinking physical copy of the arscache. Otherwise, it's just not possible (with NFS for example). Thank you for the precision and warning you are 10000% right :-D

@ Pankaj, I was just speaking about the arscache yes. Nothing about TSM and its cache... Only pure and clean OnDemand cache !
If you want to "copy" TSM from server1 to server2, just copy the corresponding storage nodes/sets from server1 to server2 (need to have a lot of disk/tape space if you have a lot of archived documents), point the second CMOD server (not the prod, the DR :-D) to the new tsm server (dsm.sys/dsm.opt/ars.cfg)... and you're set.
And of course as Justin said for the cache, Do not share the same TSM storage node between several CMOD Server... otherwise the results could be unpredictibable, meaning you cannot ensure that your documents will be in sync with the DB.

Cheers,
Alessandro

[rajeshmutha]

Justin and Alessandro,
    Here is what we are trying to accomplish. We are supposed to migrate the documents from server1 to a server2 (which is going to be a consolidated CMOD server consisting all the docs across board).
    Since server1 is cmod prod live server which has a lot of loadings and retrievals, we are trying to setup a new cmod server3 with the same cmod database as in server1.
With this we are trying to achieve following:
    1. When we are searching for the docs on server3, there will be no load on server1 cmod data base.
    2. But when extracting the document after search we want cmod on server3 to point to server1 cache and server1 tsm

Thanks, Rajesh

[rajeshmutha]

Justin and Alessandro,
Here is what we cannot do at the movement.
    1. Replicating the entire and tsm on server3 since size of the data is very huge.
    2. Cross mounting the cache and tsm file systems as it is not allowed as per enterprise standard
Is there a way to point to the server1 cache and tsm from server3?

Thanks Rajesh

[Alessandro Perucchi]

Hello Rajesh,

Ok, If I understand correctly, you want a server for the load (server1), and a server for the query (server3).
Is that correct?

I think the solution you are trying to do is not very good with CMOD, because the architecture is not made for such extreme case as you tried to implement.

That said, I hope you are doing a DB sync server1 -> server3 every day. Otherwise it won't make sense.
Next I would advise to copy as is the whole cache from server1 -> server3. NFS, cross mounting.... is not an option, you will have more problems than solutions. Use some rsync and KEEP THE LINKS AS LINKS!
Point server1 and server3 to your TSM, with the STRICT RULE that server1 is doing loads/unload, and server3 is doing ONLY searches.

Then concerning the System Logs... You have a problem here, because in such configuration, you will mix the TSM entries with 2 system writing on it (if they need to write documents in TSM), and you'll loose the server3 info concerning the user usages. So in that case, you won't be able to keep a correct log activity... for compliance and auditing, that would be certainly a NO-NO... (at least in Switzerland, if we play and loose half of the logs... we're dead  !)

So this play you are trying to do, would be nearly OK, except for the "System *" logs... because they are doing (at least System Logs) loads of log documents for some entries...

Cheers,
Alessandro

[pankaj.puranik]

Alessandro

What about Swiss banks that have offices in USA ... Just kidding!!