I’ve been a fan of the Single Instance Storage groveler since I figured out what the heck it was way back in Windows 2003 land. It is used in quite a few systems, not the least of which is Windows itself in the file server role (if enabled as a feature in 08 and R2). Recently, I learned that Exchange 2010 was removing SIS from the product. There is a great discussion that from the MS Exchange Team on their blog which can be found here that ALMOST convinces me that it was a good idea.
First a quick recap on what SIS does: Just that – pretty simple – single instance storage of objects. If you have two files on the hard drive and they are identical in every way, the file server stores only one copy and you get something that resembles a pointer (but it isn’t a pointer) on the FS to save space. In Exchange, it makes even more sense because every dummy with a forward button finds it necessary for whatever reason to forward that 5 meg Excel spreadsheet to the entire company instead of putting the file in SharePoint, but I digressed. (I tend to do that a lot)
I read through this article with a fine tooth comb and came to the conclusion that the logic of the team in deprecating this essential feature is flawed. The main argument is that storage space is no longer a premium and that it is somehow acceptable to store multiple copies of attachments in the store. While I do agree that storage space is less of a premium and that most organizations split their content databases such that SIS benefits are minimized, I believe that there are ample examples of organizations that do benefit strongly from SIS, and its removal, while probably a practical necessity, will cause pain points.
An example of potential problems will crop up in the SMB space…say, 100 employees. They are just big enough to do their own Exchange environment, but the installation is kept necessarily simple. That environment includes local replication for redundancy of the data store, but only has a single storage group. That won’t be a recommended approach for recoverability but it is a reality. Take further this example company that hasn’t seen the light and moved to SharePoint collaboration and they still forward around multiple copies of files, some quite large, and actually use (shudder) their email inbox as a version control system. It’s nasty but IT HAPPENS. I would never suggest this approach but being the pragmatist that I am – well, SIS was a lifesaver. Not anymore.
This being said, the article was a great read, explained the reasons extensively, but I think fails to account for the fact that not every deployment fits into the best practices arena and those too have to be supported.