I understand that for barriers to work, the fs needs to be able to tell the drive when to move data from hardware cache to the platter. I notice various pages mention the SYNCHRONIZE CACHE command (SCSI) and the FLUSH_CACHE_EXT command (ATA) as if they are equivalent. Looking more closely, I found the SYNCHRONIZE CACHE supports a block range, whereas it appears that FLUSH_CACHE_EXT always flushes the entire cache (maybe 32MB or 64MB on a SATA drive) Does ext4 always flush all of the cache contents? Or if the system is SCSI, does it only selectively flush the blocks that must be flushed to maintain coherency? -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
