Backing up that large Oracle database with Netbackup’s Snapshot client

A great thing happens when you marry-up some large storage to a large database, you can deliver a large solution. You can also give yourself a large backup headache. Let’s use Oracle for an example. One of the typical ways administrators are getting their large databases backed is by creating an Oracle backup policy which sends an RMAN stream (a humongous one) over the network. The performance of this method can often be measured with a calendar. Another method involves provisioning out a large locally attached disk volume and sending the RMAN job to the local disk that later gets backed up by a standard file system policy which, you guessed it goes over the aforementioned network. Now if your database resides on a storage array with some flavor of in-system replication then another way is to script your way through the problem. This involves writing a script(s) that manipulates the database into backup mode, leverages a sync (or resync) function on your primary and mirror disk volumes and then mounts the mirrors up on a backup server. My company has made some pretty nice scratch doing this and it does work well. Until that is your storage administrator has decided to change job fields and go into farming (it’s happened) and the database administrator is a contractor who may or may not have a firm grasp on the nuances of RMAN which by now may have you in a mild panic trying to figure how to get it all working again. There are other methods of course but using my own polling (unofficial of course); these seem to be the running favorites.

Symantec’s Veritas Netbackup folks have taken up the challenge of backing up very large databases (VLDB) leveraging some advanced storage array replication features and it’s called Snapshot Client (formerly Advanced Client). What is it and how does it work? With the alternate client backup feature, all backup processing is offloaded to another server (or client). This off-loads the work to an alternate system significantly reducing computing overhead on the primary client. The alternate host handles the backup I/O processing so the backup process has little or no impact on the primary client. A NetBackup master server is connected by means of a local or wide-area network to target client hosts and a media server. The primary NetBackup client contains the data to be backed up. A snapshot of that data is created on the alternate client (or media server). The alternate client creates a backup image from the snapshot, using original path names and streams the image to the media server. Trivia question – Does Oracle have to be installed on the media server (alternate client)? The answer is No. The snapshot client will call RMAN using the same Netbackup wrapper script it has always used but leverages Oracle’s remote proxy copy RMAN option. I’ve included an example with the proxy option here for you:


RUN {
ALLOCATE CHANNEL ch00 TYPE 'SBT_TAPE';
ALLOCATE CHANNEL ch01 TYPE 'SBT_TAPE';
BACKUP
PROXY
SKIP INACCESSIBLE
TAG hot_db_bk_proxy
# recommended format
FORMAT 'bk_%s_%p_%t'
DATABASE;
sql 'alter system archive log current';
RELEASE CHANNEL ch00;
RELEASE CHANNEL ch01;
# backup all archive logs
ALLOCATE CHANNEL ch00 TYPE 'SBT_TAPE';
ALLOCATE CHANNEL ch01 TYPE 'SBT_TAPE';
BACKUP
FILESPERSET 20
FORMAT 'al_%s_%p_%t'
ARCHIVELOG ALL DELETE INPUT;
RELEASE CHANNEL ch00;
RELEASE CHANNEL ch01;
ALLOCATE CHANNEL FOR MAINTENANCE TYPE SBT_TAPE;
CROSSCHECK BACKUPSET;
DELETE NOPROMPT EXPIRED BACKUPSET;
RELEASE CHANNEL;


Now before running off down the hall yelling I am delivered! I am required by professional ethics (and common sense) to mention a few caveats. This method does eliminate all the custom scripting which invariably becomes a hindrance when you start having staff turnover or when something breaks. The snapshot method replaces it with commercial off the shelf (COTS) software so when it breaks a call to support is your lifeline. The snapshot client does not however eliminate the need for staff trained in multiple disciplines (DBA, Storage, Backup) to make it work. Sorry the days of “take the default, click next, click next” are not right around the corner for VLDB’s.

My primary product mix experience involving the snapshot client is with Hitachi ShadowImage, Oracle and Netbackup Enterprise Server. The actual product support matrix is quite extensive so for those EMC, IBM and NetApp users out there you now have some options.

Backing up that large Oracle database with Netbackup’s Snapshot client