In 2008, SQL can 'repair' damaged pages from the mirror automatically. Enterprise edition only.
A database mirroring partner running on SQL Server 2008 Enterprise or later versions automatically tries to resolve certain types of errors that prevent reading a data page. The partner that is unable to read a page requests a fresh copy from the other partner. If this request succeeds, the unreadable page is replaced by the copy, which usually resolves the error.
If you're using standard edition, I think you'd have to use backups (though you could take a backup of the mirror and use that). Doesn't have to be the entire database, a single page restore should work.
Not all pages types can be repaired from the mirror and not all page types are eligible for single page restore.
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