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Red Hat Enterprise Linux 9 Essentials Book now available.

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Red Hat Enterprise Linux 9 Essentials Print and eBook (PDF) editions contain 34 chapters and 298 pages

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17.2. Enabling/Disabling Write Barriers

To mitigate the risk of data corruption during power loss, some storage devices use battery-backed write caches. Generally, high-end arrays and some hardware controllers use battery-backed write cached. However, because the cache's volatility is not visible to the kernel, Red Hat Enterprise Linux 6 enables write barriers by default on all supported journaling file systems.

Note

Write caches are designed to increase I/O performance. However, enabling write barriers means constantly flushing these caches, which can significantly reduce performance.
For devices with non-volatile, battery-backed write caches and those with write-caching disabled, you can safely disable write barriers at mount time using the -o nobarrier option for mount. However, some devices do not support write barriers; such devices will log an error message to /var/log/messages (refer to Table 17.1, “Write barrier error messages per file system”).
Table 17.1. Write barrier error messages per file system
File System Error Message
ext3/ext4 JBD: barrier-based sync failed on device - disabling barriers
XFS Filesystem device - Disabling barriers, trial barrier write failed
btrfs btrfs: disabling barriers on dev device


 
 
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