IT Departments over the past few years dedicated physical servers as per application requirements. In this process disk storage was associated with each server as direct attached, network attached, or storage area network storage. Software based backup application agents resided on each physical server and each night the changed files associated with each physical server’s dedicated storage were copied to either a disk or a tape. In most cases on the data was backed-up and very rarely did imaged-based backup for bare metal restores was practiced.
But now server virtualization has changed this trend on a drastic note. IT Data Centers are rapidly moving to a virtualized server world using VMware, Hyper-V and other hypervisors. In this process, the virtual server uses direct attached storage, network attached storage or storage area network. However, the backup application no longer backs up just the data but rather backs up the entire Virtual Machine (VM).
A Virtual machine includes the guest operating system, the application, and all the system files associated along with the data. So, with this composure way to backup the entire VM, a change in the way you need to think about backup can be attained.
However, with these VM backups, an increase in the amount of required backup storage is observed, as in the virtual world the same amount of storage is not possible to allot like in the physical server world.
But logically speaking, there is a benefit to require an increase in backup storage. In the past, if a primary server failed for any reason, you would obtain a new server, load the server with all the software or copy an image of the server for future usage. It is only after completing the said process, was the restoration of most recent data possible.
But in the virtual world, VM Backups are typically written to disk. Since the Virtual machine is sitting on backup disk, you can simply boot it from the backup system and achieve your backup needs. Thus, by doing so, if the primary system fails, you can boot a VM off the backup system and users can continue to work directly off the backup system. Once the hypervisor is used to make the primary system operational, the user activity is transparently moved back to the primary systems. This feature is called as VM Instant Recovery and it allows your recovery possible just within few minutes unlike hours seen in physical server environment.
If a third party(TP) auditor is auditing your data continuity plan, you can boot a VM off the backup system in order to demonstrate that you have a working copy of the entire virtual machine, including data.
In the past, showing a TP auditor the ability to recover your business was a tedious task and was infact impossible to convince. But with the help of virtualization, it is now possible for the IT head to show an auditor that you could recover from a failure. In the VM world, you can simply boot the VM off the backup disk, show the auditor that it is running, and the audit is complete. This is called as a Verified or Sure Backup.
On an additional note, since VMs are sitting in the backup system, the IT admin can boot the VM, apply a patch, and test to see the impact, before rolling it out in the primary virtualized environment. Thus, a virtual lab creation is possible if the need arises.
It is a known fact that by changing a backup from backing up just the data to backing up the entire VM also changes your backup infrastructure environment and process. Thus, in virtualized environments, the changed storage blocks are tracked by the hypervisor. This is called changed block tracking. The backup app picks up the changed blocks and copies them to the backup storage target. Unlike traditional physical server backup where a full backup is performed on every weekend, in virtualized world each backup is the changed block only.
Although, they are number of benefits by going for this practice, there is still a bit of risk in doing so. If you retain too many CBT backups, the time to restore is painful. In addition, if a block is damaged or corrupted anywhere in the chain, reconstitution of full backup will fail. So, the remedy is to create a full backup, sometimes called as synthetic full backup, once in a week.
Now for those, who tend to go for a tape instead of disk in their backup solution, here’s a fact to update. Booting VMs for instant recovery, for auditory needs, testing software changes and updating outside production is only possible in disk based solutions than the ones filled with tapes, as one cannot easily read/write from tape.
With a changed block tracking feature, most VM backup applications with a weekly synthetic fill will see a storage reduction of 2:1 to as much as 6:1. As the retention period grows, so does the disk storage. With the retention period of 4 to 6 copies or greater the amount of disk storage required becomes quite costly very quickly. Therefore, for 4 to 6 copies of retention or less, straight disk can be used.
In the presence of large number of copies, disk-based backup appliances with data-deduplication are required. Data dedup enriched appliances can raise the rate of deduplication in virtualized environments to as much as 20:1. As a result, far less disk is used, and the cost to store a large number of copies for retention is far less using dedicated appliances with data deduplication versus using straight disk.
However, when using a disk appliance with data deduplication, there still needs to be a high speed disk cache in order to store full version VMs for booting for many scenarios or to be able to easily perform a synthetic full backup. Getting deep into the summary of disk-based backup appliances, the first deduplicates the data inline, which means dedup occurs on the way to disk and therefore only stores deduplicated data. In order to boot a VM, one needs to put a straight disk storage cache in front of the appliance in order to have full VMs ready to boot and then have a longer-term deduplicated storage in the appliance. The second type of appliance has both built-in to a single integrated appliance. These appliances have a disk cache or landing zones in order to maintain the most recent VMs in their full form ready to be booted or restored and then store all the deduplicated data behind that.
Backup has changed from backing up data to backing up complete virtualized machines, ultimately changing how you set up and store backups and how much backup storage is required.
One of the reliable breed of storage vendors which offers VM based backup appliances is StoneFly, Inc. It offers a backup and disaster recovery appliance called DR365 which is an ideal purpose built hyper converged infrastructure solution that can consolidate all of server, storage and backup system needs into one easy to manage appliance.
For more details call 510.265.1616 or click on StoneFly DR365.