Microsoft use Single Instance Storage on All of Their FIle Servers

Single Instance Storage (SIS) – what’s that? Single Instance Storage is when duplicate copies of a file on a file system are stored only once, with pointers to the location in the various directories. In this context we are talking about the file system. For anyone who has any Exchange experience – it’s the same concept, but on a file server.

I have been aware that SIS has been available in Windows for some time now, apparently since Windows 2000, but no-one I know has used it. I always thought that the issue was support from third parties, particularly backup vendors.

At Tech-ED this time the Windows 2003 R2 Storage Server team stated that all of Microsoft’s file servers ran SIS and that it was saving them loads of money. Over the last few weeks I’ve been ferreting around trying to find out what the story is; and yes Microsoft are running all of their managed file servers with SIS.

It turns out that the main reason SIS wasn’t being widely promoted (or widely adopted) was because there wasn’t really an administration interface for it. That’s been fixed in Windows 2003 R2 Storage Server and Microsoft are going to start promoting it’s usage. I’m not sure whether they are going to port the Administration Interface to other Windows versions, I’ll have to get that Windows Server 2003 R2 box built to have a look.

My experience with file servers would give duplicate file numbers lower to the ones the Microsoft experience. They experience a saving of 60%, I’d put it nearer 40% but it’s still a load of storage and associated backup that is being saved.