Search problems with large SharePoint groups

Had a problem where the search facility was indexing some site collections but not others - even though they were in the same namespace (i.e., couldn't have been proxy exceptions, etc.).

The crawl log listed errors against the site collection URLs saying "Element Not Found". The gather logs also reported the following for each site collection URL:

10/09/2007 13:20:14.37 mssdmn.exe (0x0424) 0x0E04 Search Server Common PHSts 0 Monitorable STS3::COWSSecurityObject::AddUserToACLs: Return error to caller, hr=80070057 - File:d:\office\source\search\search\gather\protocols\sts3\sts3util.cxx Line:1637
10/09/2007 13:20:14.37 mssdmn.exe (0x0424) 0x0E04 Search Server Common PHSts 0 Monitorable STS3::COWSSecurityObject::Init: Return error to caller, hr=80070057 - File:d:\office\source\search\search\gather\protocols\sts3\sts3util.cxx Line:1396
10/09/2007 13:20:14.37 mssdmn.exe (0x0424) 0x0E04 Search Server Common PHSts 0 Monitorable STS3::COWSSite::AddScope: Return error to caller, hr=80070057 - File:d:\office\source\search\search\gather\protocols\sts3\sts3util.cxx Line:1171
10/09/2007 13:20:14.37 mssdmn.exe (0x0424) 0x0E04 Search Server Common PHSts 0 Monitorable STS3::COWSSubWeb::InitSecurity: Return error to caller, hr=80070057 - File:d:\office\source\search\search\gather\protocols\sts3\sts3util.cxx Line:2332
10/09/2007 13:20:14.37 mssdmn.exe (0x0424) 0x0E04 Search Server Common PHSts 0 Monitorable STS3::COWSSubWeb::Initialize: Return error to caller, hr=80070057 - File:d:\office\source\search\search\gather\protocols\sts3\sts3util.cxx Line:2163
10/09/2007 13:20:14.37 mssdmn.exe (0x0424) 0x0E04 Search Server Common PHSts 0 Monitorable CSTS3Accessor::InitURLType: Return error to caller, hr=80070057 - File:d:\office\source\search\search\gather\protocols\sts3\sts3acc.cxx Line:1500
10/09/2007 13:20:14.37 mssdmn.exe (0x0424) 0x0E04 Search Server Common PHSts 0 Monitorable CSTS3Accessor::InitURLType fails, Url sts3s://portal.edulink.internal/siteurl=/siteid={6b5da8a8-fdb4-419f-a82d-aaef67d6c7a9}/weburl=/webid={e480f6f1-472e-4770-9b70-2115c1089400}, hr=80070057 - File:d:\office\source\search\search\gather\protocols\sts3\sts3acc.cxx Line:172
10/09/2007 13:20:14.37 mssdmn.exe (0x0424) 0x0E04 Search Server Common PHSts 0 Monitorable CSTS3Accessor::Init fails, Url sts3s://portal.edulink.internal/siteurl=/siteid={6b5da8a8-fdb4-419f-a82d-aaef67d6c7a9}/weburl=/webid={e480f6f1-472e-4770-9b70-2115c1089400}, hr=80070057 - File:d:\office\source\search\search\gather\protocols\sts3\sts3handler.cxx Line:238
10/09/2007 13:20:14.37 mssdmn.exe (0x0424) 0x0E04 Search Server Common PHSts 0 Monitorable CSTS3Handler::CreateAccessorExB: Return error to caller, hr=80070057 - File:d:\office\source\search\search\gather\protocols\sts3\sts3handler.cxx Line:256

The problem was a SharePoint group present in the top level site of each site collection with membership of just over 1900 accounts. I removed the group in each top level site and this resolved the issue.

The "Plan for software boundaries" guide at http://technet2.microsoft.com/Office/en-us/library/6a13cd9f-4b44-40d6-85aa-c70a8e5c34fe1033.mspx?mfr=true suggests a limit of 2,000 security principals per Web site, so it could be this. However, the users still existed in the site collection after I removed the group, so it was probably related to the number of users in the SharePoint group instead.