To clarify, if your company sells (or wholesales) e-mail services to subscribers, how over-committed are your physical disk resources? Do you maintain enough physical capacity to serve 100% of assigned quotas? 50%? 10%? 1%?

Additionally, how much physical disk space does your average e-mail subscriber utilize?

* This was selected as Best Answer

Matt,

It depends if the service is provided as a shared or dedicated (hosted) model. In a shared model, I don’t usually see any “major” over commits on storage. The storage is provisioned in large chunks (200GB) as needed. Most service providers are looking at email archiving technologies to insert stubs into the primary message store and relocate the bits of the mail messages to tier 2 storage devices.They can see major savings on successful archiving that is transparent to their end users and they can eliminate quotas and charge an up-tick for the archiving service, especially if there are web portal type searching and full indexing included at the archive tier. The archive operation (if they are working with real archival technology) also takes the data out of poorly designed databases, or better stated, databases that were never anticipated to manage the volume and growth of email data and attachments that is prevalent with todays usage and relocate the data to file systems which are easier to manage from a storage, replication, backup, disaster recovery perspective.

In the hosted instance, I see huge over commits on storage. On day one standing up a 12TB Centera frame for example, the catch is that the costs are almost always passed onto the customer, so I’m not sure if that is considered waste from the financial aspect.

The question is timely, as I see that most of the larger providers (those servicing 2mil+ mailboxes) are looking to move their storage providers into a (JIT) Just-in-Time management philosophy, so they can floor the storage, but only pay once it is used, so there is minimum waste.

For email usage IBM has a good write-up where they classify users as light, medium, heavy and power users of email with stats for each. Below is a snipit of the overall write-up. You can find the full paper here:

http://www.ibm.com/developerworks/lotus/library/domino-mail-sizing/

Light users
Light users use email only without the scheduling feature of calendar. They may occasionally receive appointment notices, but never schedule meetings themselves. They never send/receive email attachments and have message sizes of 10 KB or less. They send or receive no more than 10 messages/day (including Internet mail), evenly distributed throughout the day. Mail files for light users are under 50 MB. Users who start out as light quickly learn more about the product and advance to become medium users, so for correct sizing, you should not overestimate the number of light users.

Medium users
Medium users use email together with light calendar and scheduling (C&S) functionality (one or fewer appointments/day). They occasionally send/receive mail with small attachments or graphics. Their average message size is 25 KB with most messages under 100 KB, and they send/receive 10 to 25 messages/day. Their mail file sizes range from 50 to 200 MB. Most users fall into this category. If you're not certain of your users' work habits, choose this category of user activity.

Heavy users
Heavy users exploit more email and C&S functionality (five or more appointments/week) than medium users. Their message sizes are larger (50 KB on average), and most mail messages are under 500 KB. Heavy users send/receive 26 to 40 messages/day, and their mail file sizes are greater than 200 MB.

Power users
...The average message size for a power user is 75 KB, but the typical message size is 100 KB or more. Power users have 10 or more appointments/week, send/receive more than 40 messages/day, and their mail file sizes are greater than 200 MB. Generally speaking, relatively few users in your community should fall into this category.

Good Luck,
Peter
March 2008

Links:

* http://www.ibm.com/developerworks/lotus/library/domino-mail-sizing/