SAN Client fact and fiction

The SAN client was introduced in NetBackup 6.5 to allow large amounts of data to backed up rapidly over SAN connections rather than using LANs. The SAN client has distinct advantages over both the LAN client and the SAN media server . The SAN client is much easier to administer and operate the a SAN media server as no devices are presented directly to the server being backed up. It also offers significantly faster transfer rates that Gbit LAN connections allow (testing with 4 Gbit HBAs has shown transfer speeds of the order of 500 Mbytes/sec). In the initial 6.5 GA release the SAN client was limited to 2 Gbit fibre connections and could only back up to disk on the media server.

Both of these restrictions were removed in NetBackup 6.5.2 when backup direct to tape and support for 4Gbit HBAs was introduced. The platform coverage for FT Media Servers to support the SAN client was also extended. The SAN client can be used with most standard NetBackup clients and uses either Solaris of Linux media servers. It also supports the use of most application agents including Oracle, Exchange and MS-SQL.

There are some limitations around the SAN client but these are not as significant as most people believe. The most well known (and frequently misunderstood) restriction is that the SAN client requires the use of Q-Logic HBA cards. While this is true it only applies to the cards used on the FT Media Server to connect to the SAN clients. The HBAs on the SAN clients themselves and the HBAs used to connect to the tape and disk storage on the FT Media Server can be from Emulex and other vendors.

The reason a Q-Logic HBA was chosen for the FT Media Server is that its open architecture enables us to replace the Q-Logic device driver with our own, Symantec developed, target mode driver. Thus although the hardware used in the FT Media Server is Q-Logic the driver software used is not.

Many people are reluctant to deploy the SAN client because of its perceived dependency on Q-Logic HBAs which have historically suffered from driver related problems, so let’s recap on those two key points again:

1. Q-Logic hardware is only needed for the FT connections on the Media Server

2. Once installed and configured the Q-Logic drivers are replaced by Symantec target mode drivers

Very little Q-Logic hardware and no Q-Logic software.

To summarise – the SAN client:

• Is easier to manage than a SAN media server

• Offers transfer speeds comparable to 10 Gbit LAN

• Supports most NetBackup clients and agents

• Has a small dependency on Q-Logic hardware but no dependency on Q-Logic software

Converting existing SAN media servers to SAN clients is a relatively simple exercise and the reduced administration overhead resulting from the conversion process improves the scalability of NetBackup.