When it come to understanding how much disk space you'll need in your overall disk space topology, I've developed a model to help you calculate this. Remember, this is a model, not a formula. Plug in your numbers and you'll see what I mean. I base my numbers on 1GB of raw, uncompressed data that you're going to upload into SharePoint.

First, for the data, you'll need 1GB of disk space.

Secondly, you'll need 10% for the index times the number of Index and Query Servers. For example, if you have one index and three query servers, then you'll need 10%x4.

Thirdly, you'll need ~ 30% for the metadata in SQL. Sometimes, it will be as little as 10% but can be as much as 30%.

Fourthly, you'll need free disk space equal to 100% the size of your largest database in SQL plus enough room to write the information to the transaction log

If you index any content external to SharePoint, you'll need another 10% for the index times the number of index and query servers (only one index server) and 30% for the metadata in the SQL server.

You'll need enough room to back all of this up to disk, then to tape.

	Description	Storage Capacity (GB)	Total
1	Initial capacity	1.00	1.00
2	Index & Query Servers (10%)	0.10	1.10
3	SQL Database (30%)	0.33	1.43
4	Transaction Log Sizes (50MB)	0.05	1.48
5	Free Disk Space (100%) To resize largest SQL DB	1.48	2.96
6	All other files (external - 40%)		2.96
7	Backups disk to tape	2.96	5.92

This does not account for the space necessary to build and maintain the NTFS file system.

HTH

Bill English, MVP
Mindsharp