The convosync
(convert osync) mode has the following suboptions:
convosync=closesync
Note
The convosync=closesync
mode converts synchronous and data synchronous writes to non-synchronous writes and flushes the changes to the file to disk when the file is closed.
convosync=delay
convosync=direct
convosync=dsync
Note
Use of the convosync=dsync
option violates POSIX guarantees for synchronous I/O.
convosync=unbuffered
The convosync=delay
mode causes synchronous and data synchronous writes to be delayed rather than to take effect immediately. No special action is performed when closing a file. This option effectively cancels any data integrity guarantees normally provided by opening a file with O_SYNC
.
See the open
(2), fcntl
(2), and vxfsio
(7) manual pages.
convosync=closesync
or convosync=delay
mode because they actually change synchronous I/O into non-synchronous I/O. This may cause applications that use synchronous I/O for data reliability to fail if the system crashes and synchronously written data is lost.
The convosync=direct
and convosync=unbuffered
mode convert synchronous and data synchronous reads and writes to direct reads and writes.
The convosync=dsync
mode converts synchronous writes to data synchronous writes.
As with closesync
, the direct
, unbuffered
, and dsync
modes flush changes to the file to disk when it is closed. These modes can be used to speed up applications that use synchronous I/O. Many applications that are concerned with data integrity specify the O_SYNC fcntl
in order to write the file data synchronously. However, this has the undesirable side effect of updating inode times and therefore slowing down performance. The convosync=dsync
, convosync=unbuffered
, and convosync=direct
modes alleviate this problem by allowing applications to take advantage of synchronous writes without modifying inode times as well.
convosync=dsync
, convosync=unbuffered
, or convosync=direct
, make sure that all applications that use the file system do not require synchronous inode time updates for O_SYNC
writes.