I'm attempting to upgrade a SQL 2005 SP3 clustered instance to SP4. During installation, a rollback event took place with the error indicating there was insufficient space on the the disk. The system volume and application binary volume both have adequate space. On examination of the hotfix logfile, the config.msi target folder for the rollback files was the volume used as a mountpoint folder (in this case, M: was the target but it's only 128 MB in size, hosting only folders to be used as mountpoints for other physical disks, like M:\DATA00). Why would the SP install routine use that volume instead of the system volume or SQL binary volume for the rollback file location and can the target path for the rollback file be altered?