List Attachments over 50MB need more than an increase in Maximum Upload Size...

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Chalk this down as the 1045th* time I've been reminded that you learn something new about SharePoint every day.

*The number of days I've been working with SharePoint... :)

Requirement:

  • Increase the maximum upload size for documents and attachments to 60MB for a web application

Apparent solution:

  1. Connect to Central Admin
  2. Navigate to Central Admin > Application Management > Web Application General Settings
  3. Select your web application
  4. Set the Maximum Upload Size value to 60 MB and hit OK.

Results:

  • Upload a 55MB document to a doclib - success.
  • Attach a 55MB file to a list item - receive the classic "An unknown error occurred" message, scratch head in puzzlement

Turns out there's a setting at the IIS level that will block list attachment uploads above 50MB. Below 50MB, any max upload size you pick (for example, 10MB) works fine for both list attachments and document uploads and is enforced directly through web app settings. Above 50MB, you need to make at least one minor tweak to your web.config to allow larger uploads.

Complete solution for max upload sizes over 50MB:

  1. Connect to Central Admin
  2. Navigate to Central Admin > Application Management > Web Application General Settings
  3. Select your web application
  4. Set the Maximum Upload Size value to "X" MB and hit OK.
  5. Repeat steps 6-7 for all zones for your web application on all servers hosting the web application role
  6. Open the web.config
  7. Replace the following line:
    <httpRuntime maxRequestLength="51200" />
    with
    <httpRuntime maxRequestLength="{X * 1024}" />

if you're using SQL storage for your SharePoint content, the maximum useful value for the maxRequestLength should be 2097152 (2GB in kilobytes = 2 * 1024 * 1024). Keep in mind that other limits may affect large uploads, most notably:

  • Site Collection Quota
  • Timeouts (you may need to adjust these in BOTH Web Application General Settings and the executionTimeout attribute of the <httpRuntime/> element)
    • Timeout settings will be influenced by network throughput limitations like latency and available bandwidth
  • Custom Storage Solution
    • External Blob Storage solution (see WSS SDK v1.3 for this feature that's new to WSS SP1) - whatever max BLOB size applies
  • Disk Space
    • If using SQL Storage, this is the disk containing your data files for your webapp's content DBs
    • If using an External Blob Storage solution, then this is wherever your blob store resides

For more on the httpRuntime web.config element, see https://msdn2.microsoft.com/en-us/library/e1f13641(VS.80).aspx .