Hi, I am working on storage requirement projection for next few years and have a question about log/database relationship. If a MBX server generated 50GB per week. How much will it add to the mailstore when the logs are fully committed after consider the impact of database/index overhead? Retention is set to 60 days without single-item-recovery. thanks

Hi, You can use Exchange2010 calculator for understanding disk spaceExchange Queries

Hi The transaction log files are a record of every transaction performed by the database engine. All transactions are written to the log first, and then lazily written to the database. Unlike Exchange Server 2003, the transaction log files in Exchange 2010 have been reduced in size from 5 MB to 1 MB. This change was made to support the continuous replication features and to minimize the amount of data loss if primary storage fails. You can use the following table to estimate the number of transaction logs that are generated on an Exchange 2010 Mailbox server where the average message size is 75 KB. The value for Number of transaction logs generated per day is based on the message profile selected and the average message size. It indicates how many transaction logs will be generated per mailbox per day. The log generation numbers per message profile account for: Message size impact Amount of data sent/received Database health maintenance operations Records Management operations Data stored in a mailbox that is not a message (tasks, local calendar appointments, contacts) Forced log rollover (a mechanism that periodically closes the current transaction log file) Terence Yu TechNet Community Support

Number of transaction logs generated per mailbox profile Message profile (75 KB average message size) Number of transaction logs generated per day 50 10 100 20 150 30 200 40 250 50 300 60 350 70 400 80 450 90 500 100 Terence Yu TechNet Community Support

You can use the following guidelines to understand how message size affects the generation rate of transaction logs: If the average message size doubles to 150 KB, the logs generated per mailbox increases by a factor of 1.9. This number represents the percentage of the database that contains the attachments and message tables (message bodies and attachments). Thereafter, as message size doubles beyond 150 KB, the log generation rate per mailbox also doubles, increasing from 1.9 to 3.8. For example, if you have a 100 messages per day and: An average message size of 150 KB, the logs generated per mailbox are 20 1.9 = 38. An average message size of 300 KB, the logs generated per mailbox are 20 3.8 = 76. The following sections discuss factors that affect your log sizing capacity: Backup and restore factors Move mailbox operations Log growth overhead High availability factors LUN capacity planning Understanding Mailbox Database and Log Capacity Factors If you need example, you can read this example. Exchange 2010 Mailbox Server Role Design Example Terence Yu TechNet Community Support