Estimating database size

The size of the database depends on the application, as well as the number of users and items. A database containing the seed data supplied with the Movie Site application may use just 250 MB, while the LikeMinds tables for a large site with millions of users may take up 10 GB. This section presents some general guidelines for estimating the size of the database, but the results may vary.

The tables that contribute the most to the size of the database are as follows:

• Lps_User_Rating: This table normally dominates the space considerations. Users typically average 50 to 100 ratings. The seed users supplied with Movie Site average about 500 ratings.

• Lps_User_Trx: This table can grow very large, depending on the number of item affinity, clickstream, or purchase activities recorded from our applications.

• Lps_MBA_Scored: This table can grow quite large, depending on the number of products the site sells and the number of relationships you want to configure for each product. For example, if you have 1000 products listed in the Lps_Item_Data table, and you want to store 10 relationships for each product, an Lps_MBA_Scored table can grow to 10,000 rows.

• Lps_User_Mentor: The size of this table depends on the number of users and the number of mentors associated with each user (50 by default).

• Lps_User_Data: This table may contribute a large portion of the database size if you have large numbers of users who each have few ratings. This table is heavily indexed, which can affect performance.

• Lps_Item_Data: This table is normally fairly small, but may be significant if you store large amounts of data about each item.

The remaining tables are typically less than 100 KB each.

The following table gives typical numbers of rows, row sizes, and index sizes for a "typical" Microsoft SQL Server database with 5000 items and 100,000 users. The row sizes include only the fields required by LikeMinds, and they account for typical null fields and clustered index overhead. Sizes will vary for other database systems, especially for indexes.

Table 1. Example Table Sizes for a Typical Database

Table	Rows in Typical Site	Row Size (Bytes)	Total Size	Index Size (Bytes Per Row)	Total Size
Lps_User_Rating	8,000,000	25	200 MB	about 20	160 MB
Lps_User_Trx	8,000,000	32	256 MB	about 20	160 MB
Lps_User_Mentor	5,000,000	25	125 MB	about 20	100 MB
Lps_User_Data	100,000	typical: 100 maximum: 400	100-400MB	about 100	10 MB
Lps_Item_Data	5000	136 (for required fields only)	68 MB	4	2 MB
Lps_MBA_Scored	10,000	32	32 MB	about 20	1MB
Lps_Genre_Data	10-1000	116	1160 KB-116 MB		N/A
Lps_Item_Genre	5000-20,000	12	60-240MB		N/A
Lps_User_Selector	25,000-100,000	12	30-120MB	4	100-400 MB

In the size estimate, remember to include space for transaction logging and rollback areas. Because the LikeMinds server commits frequently, the rollback area need not be especially large relative to the database. Allow space equal to the size of the database for transaction logs, since the LikeMinds server performs frequent updates.

 

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