Home > Backup > When Snapshots with Replication Aren’t Enough: Benefits of a Purpose-built Backup Solution

When Snapshots with Replication Aren’t Enough: Benefits of a Purpose-built Backup Solution

When I work with customers on a storage solution, I often end up talking about backup as well. Why is that? For starters, it’s important to remember that every GB of storage you add is another GB that will have to be backed up by your backup infrastructure.

When I worked at a large pharmaceutical company, this was a problem we often encountered when internal business units would purchase more storage. Six months later as they consumed the new storage, we’d have a disaster on our hands with not enough tapes or tape drives to get backups completed. Of course, you can ask the business for more money to buy additional backup infrastructure, but that is a difficult thing to do after the original purchase. One question I often hear from customers who are looking at a multiple vendors as part of a storage/backup project is, “Why not just use snapshots with my storage array so that I don’t need a backup solution anymore?”

There are different ways to achieve “backup.” Some customers choose to use a true purpose-built backup solution, and some have chosen to eliminate backup by using snapshots with replication. Regardless of which way you decide is the correct fit for your environment, there is a solution that can meet your requirements. The majority of customers I work with choose to implement a true purpose-built backup solution as a means to achieve data protection. The entire backup de-duplication market is experiencing high double-digit growth rate every year, or even triple-digit growth in some cases. This validates that purpose-built backup solutions, leveraging de-duplication technology, are very relevant in the marketplace today.

That being said, eliminating backups by using snaps with replication will work as a way to achieve a backup of your data. You will typically hear about this method of backup from vendors that only offer storage products rather than storage and backup solutions. However, there are caveats to using this method to eliminate backup, regardless of vendor. Like anything, there are pros and cons of different data protection methodologies. Most commonly, customers wanting to do snaps with replication as a form of backup do so because they see the potential for cost savings. Adding some incremental enhancements to a storage investment that allow it to be used as a backup solution can appear to be more cost-effective than purchasing two separate solutions for storage and backup.  However, I typically find that the majority of customers still choose to implement backup with a purpose-built solution and here are some of the top reasons why they do:

1) At least 85 percent of all restores are typical day-to-day granular file restores (compared to complete server or site recovery). With a LUN snapshot, a file restore on a server becomes more complex. For a simple file restore to an app server, you must take the snap and mount it up to a server, then drill-down into the snap to recover the file and copy it back to the original location. Then, the LUN must be unmounted.  Some vendors have tools to help automate this, but it’s still not a trivial task. Snapshots are organized by snapshot date—not by files or directories in a server. If a user asks for a file to be restored, and they don’ t know what server it lived on, how are you going to find the right snapshot? There is no equivalent of a backup catalog (some 3rd parties sell software to add catalog-like functions, but that increases cost).  Compare this to opening a backup software console, pick the server, pick the date to restore to, and select the file name (or search for a file name). The file will then be restored back to the original server. This is a simpler task, plus it is very similar to the way that backup administrators do their job today, which means less re-training for staff.

2) The “snaps with replication” methodology only covers servers that are on the SAN. Therefore, a customer may end up having to use different methods of backup for servers on the SAN vs. servers that continue to use internal storage. This makes administration more complex for a backup administrator.

3) There is a greater risk of data loss from not having a secondary copy of the data stored on a different medium. While most customers will never see this, there is always the potential for a file system or LUN to get corrupted in some way, shape, or form. If that happens, and the corruption gets replicated to the secondary side, all snapshots become worthless because snapshots contain pointers that are dependent upon the primary copy of the data. At that point, there will be data loss. A secondary copy of your data stored on a different medium, whether it be classic tape or a next-gen backup solution will not be affected by this.  Solutions like Avamar and DataDomain also do data integrity checks, which does not happen on any SAN/NAS or tape product. On a SAN/NAS or tape solution, you may not realize you have corruption until you try to restore and encounter a bad block.

4) Humans are prone to make mistakes and there is a greater risk of data loss from human error using the “snaps with replication” methodology.  If there is an accidental misconfiguration of LUN replication, it is not as apparent to administrators as a failed backup job, therefore the problem may not be detected until it is too late and there is data loss. Another example might involve a newly created LUN that does not get added to a replication policy, therefore tens of VM’s could be affected because bits and pieces of the VM’s happen to reside on that particular LUN, which is part of a VMFS datastore. While human mishaps can occur in the traditional backup world, they generally would only affect one server at a time rather than multiple servers.

5) You can achieve greater retention with a true backup solution than you can with keeping snapshots.  While you may only need to keep backups for 45 days today, if those requirements increase to one year or more in the future, the snapshot methodology becomes less attractive. The longer you keep snapshots, the more space they require, and the more overhead is required to keep track of all the delta changes in the snapshot. It is not best practice to keep snapshots for longer-term data protection (several months to 1yr+) regardless of vendor. This is best suited for a purpose-built backup solution.

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