Re: ext4 barrier on SCSI vs SATA?
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On 05/14/12 11:02, Jan Kara wrote:
However the flush was always available (I think), in fact databases would not corrupt (not even above ext4 nobarrier, above a raid5 without barriers) if fsync was called at proper times.This is not true. Both cache flushes and barriers were implemented by the same mechanism in older kernels. Thus if the device did not properly propagate the barrier capability, then fsync did not provide any guarantees in case of power failure (if there are volalile write caches in the storage device).
Oh! Thanks I had not realized this.So, if barrier IS provided by the underlying blockdevice but filesystem is nevertheless mounted as nobarrier (as an explicit option) would database flushes (fsync) for files on THAT filesystem work properly or not?
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