Slinger's Thoughts

March 20, 2013

Target Discrimination – What do you backup?

Filed under: Disaster Recovery, SharePoint — slingeronline @ 12:28 pm

For those that don’t know me, I am an avid firearms enthusiast.  Handguns, Rifles, etc.  One of the things that responsible shooters practice is target discrimination.  Target Discrimination is the delicate art of hitting exactly what you want to hit, and missing exactly what you want to miss.  So how does this relate to Disaster Recovery? All too often, there is a corporate policy for Disaster Recovery that I call “Carpet Bombing.”  Everything is backed up. Everything. Hard drive snapshots are created every 6 hours. A full system image is created every night. Information that has been sitting dormant for 4 years, 7 months, and 13 days, gets backed up every night, making a new copy of the same information. Even if a backup system is advanced enough to do differential or incremental backups, an index of this unchanged file is created every time.

Perhaps it would be better to imagine this in terms of physical files, and not computer files.  You have a file cabinet that is full of thousands of documents.  Every night, it is the responsibility of one person to photocopy every single file, and then return them to their respective file drawer.  In the case of incremental and differential backups, the file itself is not copied, but the index card that says where the file is, what is in it, and when it was last changed, among other identifying features, is copied. If the change was more recent than what ever the disaster recovery policy says, the actual file is found and added to the xerox pile.  If the company policy is that no photocopies older than 7 days are allowed to be used, every 7 days every single file gets dragged out of the cabinet and photocopied again.

This is where target discrimination comes in. Some files do change, and some don’t. If the file folder for the 10 year lease on the building doesn’t ever change, why would we drag it out and create a backup of it every week? It is apparent that it doesn’t make a lot of sense in a paper world, but we do it in the computer world daily and think nothing of it.  We drag entire hard drives over to the photocopier and make a copy of the whole mess, whether they need it or not. We end up with 137 copies of the exact same file, spread across backups, taking up valuable storage space, and potentially creating a new kind of disaster.

In the paper world, there is one backup. Maybe several versions of the same file, but not many. Actual physical space was much more expensive than computer storage space, so a policy was usually created to only keep so many backup copies of a file. After a certain amount of time, they were shredded. Here is an example. Go to your file cabinet, and pull out your tax forms from 1997. You probably don’t have them anymore. There is no need for them, so they got pitched, shredded or burned in the barbecue pit. Now pull out your tax forms from last year. You still have those. You may not need them, but you have them just in case. (You should anyways.) Now, do you make a backup copy of these every week? Kind of silly to do so isn’t it? If they were computer files though, then for some reason it makes perfect sense.  This is what target discrimination is. Only backup what needs to be backed up. Discriminate the targets of your disaster recovery policy. Be selective about what gets backed up, and how often. Imagine that you have to create a physical print out of every file to get a back up, and then determine what is “mission critical” to be backed up, and what hasn’t changed since 1997.

Just like with physical paper files, it is okay to not create a backup of a file that has not changed since the last backup. Create backups of the important stuff, but let go of the theory of “we have to back up everything, everytime, just in case, just to be sure!”  When you do start discriminating your targets, you will notice something; your backups will take much less time to execute and your used storage space allocated for backups will shrink.

So how do you decide? Well, you are going to have to talk to your end users, and discuss what their needs are, and once they tell you, add what those needs are to some documentation that will govern how you manage your SharePoint farm. (I think it’s called “governance?”) Different groups in your organization are going to have different needs. Just like in your household, different aspects of paperwork have different needs. You don’t need to keep a copy of a school permission slip around for the same amount of time that you need to keep a copy of your mortgage. You probably don’t even need a backup copy of the permission slip, but should probably have several backup copies of other vital documentation, such as your mortgage.  You don’t need to keep a holiday newsletter from five years ago, but you probably should keep the financial records from five years ago handy.

A good way to determine how to discriminate your disaster recovery targets is to imagine that the files actually are physical paper.  Whatever the actual physical paper policy would be, it should be relatively simple to translate into computer disaster recovery terms.  If the file doesn’t change but once a year, you really shouldn’t feel the need to back it up once a week.

So, instead of “carpet bombing” your computer assets with a disaster recovery strategy that simply says “make backups,” a little bit of thought into discriminating what targets need to be backed up and how often, could save large amounts of storage space and system resources.  After all, you don’t need to have 137 copies of your teenage child’s 3rd grade Christmas concert program; one copy will suffice.



  1. […] the past few blog posts, I have gone over the What, When, and Where of SharePoint Disaster Recovery planning.  So, why? Why do you need any type […]

    Pingback by An Ounce of Prevention – Why Backups are important | Slinger's Thoughts — May 3, 2013 @ 2:19 pm

  2. […] you’ve been playing along, I’ve talked about what, when, where, and why you should create backups.  One you have a DR plan, that includes what […]

    Pingback by High Heels are not Hammers – How do you create backups | Slinger's Thoughts — June 10, 2013 @ 12:32 pm

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