() An attempt to determine the minimum I/O block size for the volume “” containing “” failed with system error : “”. The operation will fail with error .

Details
Product: Exchange
Event ID: 491
Source: ESE
Version: 6.5.6940.0
Component: Microsoft Exchange Extensible Storage Engine
Message: <process name> (<process id>) <storage group name>An attempt to determine the minimum I/O block size for the volume “<name>” containing “<file name>” failed with system error <error code>: “<error message>“. The operation will fail with error <error code>.
   
Explanation

You receive the following error in the Description of ESE event 491:

An attempt to determine the minimum I/O block size for the volume [drive\path] failed with [error #]. The operation will fail with error [error #].

This means that an unexpected error was encountered while trying to use the volume specified in the message. Specifically, an error occurred when an attempt to determine the minimum input/output (I/O) block size for the volume failed.

The cause depends on the Error listed at the end of the Description section of the event. The most frequent causes are listed below.

  • Error -1032 = 0xfffffbf8 = 4294966264 = JET_errFileAccessDenied = Cannot access file – the file is locked or in use. Another process has “stolen” the file. A virus checker may mistakenly quarantine a file, or a backup process may temporarily deny access. A flat file backup system or anti-virus software may be running against the database or check file directories or the M: drive. This error can also occur if the permissions on the folder that contain the files for the information stores are not sufficient for the stores to function properly.
  • Error -1022 = 0xfffffc02 = 4294966274 = JET_errDiskIO = Disk IO error. The -1022 error is a generic error that appears whenever a disk input/output (I/O) problem prevents Exchange from gaining access to a requested page in the database or to a check file. A disk or controller failure may have occurred and access to the entire drive has been lost, sometimes temporarily. The actual physical drive may be no longer accessible or have an invalid file system, such as accidentally specifying the transaction log files path to the CD-ROM drive. Check the System Log for I/O or drive errors near the time of the 491 Event. This issue may occur because the path for the check file (such as E00.chk) is not correct, which may be caused by a drive failure.
   
User Action
  • For Error -1032, change the permissions on the folders that contain the information store files to the default permissions. Configure the flat file backup and anti-virus software to not scan the Exchange server information store subdirectories or the M: drive. Use Exchange-aware online backup and anti-virus software.
  • For Error -1022, ensure that the drive for the information store files is accessible and that the path for the information store files is specified correctly. If it is, run “chkdsk /f /r” (without the quotation marks). If chkdsk does not resolve the issue, examine the permissions on the Exchsrvr folder structure. Make sure that SYSTEM has full control of Exchsrvr and all subfolders on each partition that contains Exchange data. If you still cannot mount the databases, troubleshoot any Windows NT file-level antivirus software running on the Exchange server. Check the System Log for I/O or drive errors near the time of the 490 Event. Check and correct the path for the check file (such as E00.chk).
  • After correcting the root cause, if the database is inconsistent, restore from online backup. If there is no valid backup, you can restore the database to consistency using the “hard repair” (/p) functionality of the Eseutil utility, run isinteg -fix until all fixes are removed, and then mount the database and then ExMerge to a new, blank database. NOTE: Before doing this, you should always back up all information store files in a Storage Group (*.log files, *.edb files and *.stm files).

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