NAS Appliance

Latest version: 2.3.2

	At a Glance
	Catalog	System
	Category	Misc. Appliances
	User volumes	yes
	Min. memory	64 MB
	OS	Linux
	Constraints	no
	Questions/Comments	Ask Forum

Functional Overview

The NAS appliance is a shared file storage appliance. It provides file storage accessible over HTTP, NFS, and CIFS file protocols.

The NAS appliance serves files contained within a configured (pluggable) data volume thus providing the ability for the content served by the appliance to be changed easily as well as the ability for the volume to have varied sizes. For example, if NAS is being used to store log files, the data volume does not need to be as large as what may be needed to store content for an apache server.

The root directory of the volume is shared and the HTTP, NFS, and CIFS (samba) servers see the same volume, at the same root. The NFS server exposes the volume as a shared named /mnt/data. The CIFS server exposes the volume as a share named share. The root directory of the volume is accessible for read-only access by the HTTP server and for read-write access by the NFS and CIFS (samba) server.

The security for http access may be open (no user/pwd), fixed single user/pwd (from property) or from .htpasswd file stored within the root directory of the data volume.

The CIFS access is anonymous. It is assumed that only appliances that are allowed to access the volume are connected to the cifs terminal. This eliminates the need to configure complex security settings on the client and server and makes it possible to simply connect appliances that need file access to the cifs input.

There are three key use cases for the NAS appliance:

1. Serving large files over HTTP. The cifs interface is used to add/remove files (usually exported over a separate gateway)
2. As a shared file server through which other appliances/servers exchange files (fully internal to the application)
3. As a log server through which other appliances/servers store their log files so that those logs may be easily accessed/viewed by an administrator rather than having to log into each individual appliance.

Boundary

Resources

Terminals

The default interface is enabled. This provides the ability for administrators to log into the appliance using the '3t ssh comp' command in order to perform maintenance or to troubleshoot problems. One possible maintenance activity might be to add/remove users from the .htpasswd file stored on the data volume.

User Volumes

The following file may reside within the root directory on the volume:

Properties:

Error Messages

• failed to mount data volume
• failed to set permissions on the data share
• Samba failed to start
• NFS failed to start
• Apache failed to start

Typical Usage

Static content server

The following diagram shows a typical usage of NAS for a simple web server application:

Appliances in use:

• web - input gateway, class IN
• maint - input gateway, class IN
• urlsw - URL switch, class urlsw
• admin - Linux Server, class LINUX
• nas - NAS appliance, class NAS
• apache - Apache server, class APACHE

The nas appliance in this example is used to serve the static content of the web site (e.g., images) as it is simple to configure and less resource-demanding, while a separate apache server is set up to serve the dynamic content (e.g., forms interface, etc.)

The admin appliance in this example is used to authenticate users and provide access to the cifs terminal of the nas appliance so that an administrator may update the set of files exposed by nas through its http terminal.

The urlsw appliance in this example is not shipped with AppLogic, but can be built using apache and pound. The apache appliance in this example is not shipped with AppLogic. However, AppLogic does provide a similar appliance named WEB.

HTTP Access:

web accepts HTTP requests coming to the application and passes them to urlsw through its out terminal. urlsw sends HTTP file requests for dynamic content through its out1 terminal to be served by nas1 on its http terminal. urlsw forwards all other HTTP requests through its aux terminal to be served by apache.

CIFS Access:

When an administrator needs to modify the set of files made available for HTTP access by nas, the administrator connects and logs into the admin appliance through the maint appliance. The user then mounts the CIFS share exposed by nas (if it is not already mounted) and modifies the files as needed.

Example:

Shared Storage

The following diagram shows a typical usage of NAS as shared storage for multiple application servers.

Appliances in use:

• app1 - Application server, class APP
• app2 - Application server, class APP
• nas1 - NAS appliance, class NAS

The nas1 appliance in this example is used as shared storage for app1 and app2. Both application servers have read-write access to the directories and files served by nas1.

app1 and app2 issue CIFS requests through their out terminals to the cifs terminal of nas1 in order to access files stored on the volume shared by nas1. Any changes made by one application server are seen by the other application server.

Example:

Log Server

The following diagram shows a typical usage of NAS as a log server.

Appliances in use:

• user - Input gateway, class IN
• admin - Input gateway, class IN
• webs - Load Balancer, class HLB
• srv1 - Web server, class WEB
• srv2 - Web server, class WEB
• dbase - Database server, class MYSQL
• logs - NAS appliance, class NAS
• mail - Output gateway, class OUT

The logs appliance in this example is used to store the log files for the two web servers as well as the database server and makes those files available through its http terminal.

The log terminals for the web servers (web1 and web2) and the database server (dbase) are all connected to the cifs terminal of logs so that when they write to their log files, the files are stored on the logdata volume that is configured on logs.

When an administrator needs to inspect the log files, he connects via the admin gateway to the http terminal of the logs appliance. He logs in with the configured administrator user name and password and is shown a listing of the root directory of the logdata volume from which the administrator is free to view the log file(s) he is interested in.

Example:

Notes

• The features of the http and samba servers are limited and only those features that are exposed by properties are supported. All other features of the http server that are controlled by special files stored in the document tree are disabled.
• To change the size of the data volume used by NAS, perform the following steps:
  1. Stop the application if it is running.
  2. Using the editor or 3tvol utility, create a new volume within the application with the desired size.
  3. If you want to keep the files that are on the existing volume, mount both volumes, copy the files from the old volume to the new volume and unmount both volumes.
  4. Using the editor, update the data volume for the NAS appliance to be the newly created volume.
  5. Using the editor, destroy the old volume and save the application.
  6. Start the application.

Future directions:

• add webdav and/or read-write interface through http
• add ldap authentication modes to both cifs and http

Related Documents

• Implementation Design

Questions and Comments

To post a question or comment on this appliance, visit our forum.

-- PeterNic - 30 Dec 2005