Near Zero Impact Backup and Data Replication Appliance
Original Publication Date: 2004-Oct-18
Included in the Prior Art Database: 2004-Oct-18
Storage networks and intelligent disk subsystems enable new possibilities for the backup of data. This article presents an architecture which integrates the steps for making a consistent copy of the production data using disk subsystem based snapshots (e.g., IBM FlashCopy*), continuing the application on the primary server, and backing up the copied data from a secondary server. The outlined architecture off-loads the backup data transfer from the application server to a secondary server whilst it provides support for heterogenous operating systems of the application server.
Near Zero Impact Backup and Data Replication Appliance Near Zero Impact Backup and Data Replication ApplianceNear Zero Impact Backup and Data Replication Appliance Near Zero Impact Backup and Data Replication Appliance
Background - Application server-free backup
In today IT systems more and more data (e.g. patient records, web sites) must be available around the clock. It is no longer acceptable that such data cannot be accessed during backup. The so called "application server-free backup" is a well known procedure to backup data with minimal downtime of the application, whilst it off-loads the I/O burden for the backup data transfer from the application server to the second server.
Application server-free backup exploits the instant copy feature of modern disk subsystems. Instant copies can practically copy even terabyte-sized data sets in a few seconds, and thus freeze the current state of the production data and make it available via a second access path. The production data can still be read and changed over the first access path, thus the operation of the actual application can be continued, whilst at the same time the frozen state of the data can be backed up via the second access path.
Backup using instant copy must be synchronized with the applications to be backed up. Databases and file systems buffer write accesses in the main memory in order to increase their performance. As a result, the data on the hard disk is not always in a consistent state. Data consistency is the prerequisite for restarting the application with this data set and being able to continue operation . For backup it should therefore be ensured that an instant copy with consistent data is first generated . The procedure looks something like this:
Quiesce application and flush buffers (e.g., shutdown of application and sync
Despite the quiescing and the resuming of the application the production system is back in operation very quickly.
Data protection with instant copies is even more attractive if the instant copy is controlled by the application itself: in this case the application must ensure that the data on disk is consistent and then initiate the copying operation . The application can then continue operation after a few seconds . It is no longer necessary to shutdown and restart the application.
Application server-free backup combines instant copies with a second server which is put to the side of the application server and which serves exclusively for backup (Figure 1). Both servers are directly connected to the disk subsystem which stores the production data. For backup the instant copy is first of all generated as described above: (1) shut down application; (2) generate instant copy; and (3) restart application. The instant copy can then be accessed from the second computer and the data is backed up from there without placing a load on the application server . If the instant copy is not deleted in the disk subsystem, the data can be...