Exchange 2010: Niggling Fears About Storage Requirements

Exchange 2010's database strategy is very interesting. The new Database Availability Groups and the benefits they offer for data protection and quick recovery are striking.

Overall, Microsoft is optimistic that mailboxes will be able to grow to 10GB or more. However, it's unclear how large mailboxes will perform in practice. Several concerns spring to mind:

  • By leveraging low cost disk, it is feasible, according to Microsoft, to store email online for up to 10 years. If you assume a typical user stores 5 MB of new email daily, this translates to 1.8 GB of email per year. Allowing for the continued growth in average message size, this translates to perhaps 10GB mailbox sizes over three years. For 100 users, this means 1 TB of total storage for Exchange. For 1,000 users, 10 TB of email storage! Managing multiple terabytes of storage is no simple matter when you take into account disk failures, power consumption, disaster protection, daily maintenance and monitoring, and so on
  • Database maintenance and ESEUTIL need space. Offline defragmentation requires 110% free disk space. Thus the amount of storage required should be doubled for maintenance purposes. True, Microsoft advises that offline defragging is unnecessary and inadvisable; hopefully this turns out to be wise counsel
  • If we wish to use the new Database Availability Groups for data protection and failover, extra copies will be required. Two to three copies seems likely, which implies another 2-3X in email storage
  • Single instance storage is no longer supported, which means message stores can't be shrunk by 20% or 30% or so

In a typical scenario, for every 1 TB of primary database storage, perhaps another 3-4 TB of disk space may be necessary for various support capabilities, such as Database Availability Groups. This can quickly translate into a large amount of storage.

All in all, I doubt Microsoft's claims that imply storing TB's of email data online is a simple proposition.

... Bob Spurzem

One Comment

  1. Posted December 9, 2009 at 12:37 AM | Permalink

    We (Cleartext) offer both mailbox hosting (via an Axigen ISP platform) and SaaS email archiving.

    Our strategy is to keep hosted mailboxes as low as 200-500Mb and bundle these mailboxes with the SaaS archiving service for permanent email storage. This has several advantages;

    1) Users mailboxes are easier to manage and migrate if needed and are less prone to data loss caused by IT systems issues or more often ‘user error’.

    2) The SaaS archive has full text and attachment indexing meaning it’s quicker and easy to find email when needed.

    3) The client can implement their retention policy on the SaaS platform to ensure compliance with eDiscovery regulations. Avoiding issues where staff delete email from their inbox.

    This is a change to the usual large mailbox offerings from organisation slike Google but we believe is more appropriate for business deployments.

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