Question about PowerShell syntax used in Exchange 2013 Dial Tone Restore episode

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In the Dial Tone Restore episode of Exchange 2013 Don uses a command with this syntax:

$mailboxes | %{ ... }

to initiate the restore requests for each of the mailboxes in the $mailboxes variable. It seems to me that this is the same thing that the ForEach-Object command would do. If I'm correct then command could have been entered this way:

 $mailboxes | foreach-object { ... }

It seemed, however, that Don was very careful to specify that the command needed to be entered as he showed. So my question is, how is the command, %{ ... }, different than foreach-object { ... }?

Technically, the two commands you are listed are the same. However, there is a little difference in memory handling. The foreach-object command loads everything into RAM. When restoring a mailbox server you could possible have more data than you have RAM for and the command will stall. The %{...} loop, on the other hand, moves data in/out of RAM as it is being worked with which ensures you don't have to worry about memory limits.

Hope that helps,

Don Pezet
Host, ITProTV

Yes, that's a great explanation. Thank you.