Re: File sharing in a cluster environment.

[Curt Smith <chsmith@speakeasy.net>]

Sharing from a single web server and URL?  Interesting.  What
if the web servers are clustered too?  For survivability, one
typically replicates the web content behind each clustered web
server, so this might not be the general solution.

For some folks the generalized solution that delivers resilience
to single failures is;

- redundant LAN connect points
- A SAN (storage area network) or File Share appliance that has
   built in resilience, RAID disks on the back end.

The above can be had cheaply with a semi-resilient Compaq / Dell
server (redundant power supplies and NICs) and RAID disk sub-system.
These boxes are cheaper than you might imagine.  Run Linux/Win2k

Then NFS mount or MS File share mount the resilient file share to
all your appserver boxes.

BTW, the SAN/NetAppliance folks have all sorts of architecture diags
and helps to assemble such a system, whether you decide to go professional
or cheap, either way.

I'm sure there's other viable ideas too?

Curt


Hang Ye wrote:

> Mark,
> 
>  
> 
> I had a similar problem before. The clustered app servers need to read 
> from a text file. I could simply make the file available on all boxes. 
> However, that could cause synchornization problems since the file would 
> be updated by users. Also, you have to make sure the paths to the file 
> on each box are the same. We put the file behind the web server instead 
> and the applications access it via a URL. Since it is a small file, we 
> have no performance issue here.
> 
> The key is to make a single entry to the file. URL is just a 
> workaround. Shared file system would be good. Sun provides a global file 
> system, which is a better solution. I am not aware of any utilities that 
> can sync files on the network.
> 
> Why database is a problem? Do the servers access their local db instead 
> of a global one?
> 
>  
> 
> Please let me know if you have any questions.
> 
>  
> 
> Alan
> 
>     ----- Original Message -----
> 
>     From: sarma sarraju <mailto:sarma_sarraju@yahoo.com>
> 
>     To: ajug-members@ajug.org <mailto:ajug-members@ajug.org>
> 
>     Sent: Thursday, March 14, 2002 2:04 AM
> 
>     Subject: File sharing in a cluster environment.
> 
> 
>     Hi all,
> 
>      When I am using a app server cluster to run in load balancing mode,
>     how to make sure that files in the file system are synchornised?
>     Also the how to take care of data base replication.
> 
>     I have an application which uses file system and database. Like when
>     I create a resource in this application, its going to place it in
>     file system as well as id in the database.
> 
>     When I deploy this application on web logic cluster with two
>     servers, how to make sure that what ever resource I create on one
>     server, can be accessed from the other server?. This needs file
>     system replication. We may not used shared file system.
> 
>     Any pointers are greatly appreciated.
> 
>     Thanks
> 
>     Mark
> 
> 
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-- 

Curt Smith
chsmith@speakeasy.net
(w) 404-463-0973
(h) 404-294-6686