Scenario:
How to estimate the storage space required for SharePoint 2010 content databases and index servers?
Explanation:
The following process describes how to approximately estimate the storage required for content databases, without considering log files:
1. Calculate the expected number of documents. This value is referred to as D in the formula.
How you calculate the number of documents will be determined by the features that you are using. For example, for My Site Web sites or collaboration sites, we recommend that you calculate the expected number of documents per user and multiply by the number of users. For records management or content publishing sites, you may calculate the number of documents that are managed and generated by a process.
If you are migrating from a current system, it may be easier to extrapolate your current growth rate and usage. If you are creating a new system, review your existing file shares or other repositories and estimate based on that usage rate.
How you calculate the number of documents will be determined by the features that you are using. For example, for My Site Web sites or collaboration sites, we recommend that you calculate the expected number of documents per user and multiply by the number of users. For records management or content publishing sites, you may calculate the number of documents that are managed and generated by a process.
If you are migrating from a current system, it may be easier to extrapolate your current growth rate and usage. If you are creating a new system, review your existing file shares or other repositories and estimate based on that usage rate.
2. Estimate the average size of the documents that you will be storing. This value is referred to as S in the formula. It may be worthwhile to estimate averages for different types or groups of sites. The average file size for My Site Web sites, media repositories, and different department portals can vary significantly.
3. Estimate the number of list items in the environment. This value is referred to as L in the formula.
List items are more difficult to estimate than documents. We generally use an estimate of three times the number of documents (D), but this will vary based on how you expect to use your sites.
List items are more difficult to estimate than documents. We generally use an estimate of three times the number of documents (D), but this will vary based on how you expect to use your sites.
4. Determine the approximate number of versions. Estimate the average number of versions any document in a library will have (this value will usually be much lower than the maximum allowed number of versions). This value is referred to as V in the formula.
The value of V must be above zero.
The value of V must be above zero.
5. Use the following formula to estimate the size of your content databases:
Database size = ((D × V) × S) + (10 KB × (L + (V × D)))
The value of 10 KB in the formula is a constant that roughly estimates the amount of metadata required by SharePoint Server 2010. If your system requires significant use of metadata, you may want to increase this constant.
Database size = ((D × V) × S) + (10 KB × (L + (V × D)))
The value of 10 KB in the formula is a constant that roughly estimates the amount of metadata required by SharePoint Server 2010. If your system requires significant use of metadata, you may want to increase this constant.
As an example, if you were to use the formula to estimate the amount of storage space required for the data files for a content database in a collaboration environment with the following characteristics, you would need approximately 105 GB.
Input

Value

Number of documents (D)

200,000
Calculated by assuming 10,000 users times 20 documents

Average size of documents (S)

250 KB

List items (L)

600,000

Number of noncurrent versions (V)

2
Assuming that the maximum versions allowed is 10

Database size = (((200,000 x 2)) × 250) + ((10 KB × (600,000 + (200,000 x 2))) = 110,000,000 KB or 105 GB
Microsoft recommends 80 GB of hard disk space for WFE servers. Maintain twice as much free space as you have RAM for production environments.
A quick formula to calculate the hard disk space on the index server would be to multiply the expected indexable content by 20%.
So for example if the expected total content to be indexed is 500 GB, the index server needs at least 500 * 20% = 100GB
This white paper from Microsoft explains how to estimate performance and capacity requirements for SharePoint in more detail. (page 45 for specific guidance on how to calculate storage needs for search)