Messages in this thread | | | Date | Mon, 19 Feb 2001 13:45:57 +0100 | From | David Balazic <> | Subject | Flusing caches on shutdown |
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(( CC me the replies, as I'm not subscribed to LKML ))
Hi!
It is a good idea IMO to flush the write cache of storage devices at shutdown and other critical moments. I browsed through linux-2.4.1 and see no use of the SYNCHRONIZE CACHE SCSI command ( curiously it is defined in several other files besides include/scsi/scsi.h , grep returns : drivers/scsi/pci2000.h:#define SCSIOP_SYNCHRONIZE_CACHE 0x35 drivers/scsi/psi_dale.h:#define SCSIOP_SYNCHRONIZE_CACHE 0x35 drivers/scsi/psi240i.h:#define SCSIOP_SYNCHRONIZE_CACHE 0x35 )
I couldn't find evidence to the use of the equivalent ATA command either ( FLUSH CACHE , command code E7h ). Also add ATAPI to the list. ( and all other interfaces. I checked just SCSI and ATA )
Loosing data at powerdown due to write caches have been reported, so this is no a theoretical problems. Also the journaled filesystems are safe only in theory if the journal is not stored on non-volatile memory, which is not guarantied in the current kernel.
What is the official word on this issue ? I think this is important to the "enterprise" guys, at the least.
Sincerely, david
PS: CC me , as I'm not subscribed to LKML -- David Balazic -------------- "Be excellent to each other." - Bill & Ted - - - - - - - - - - - - - - - - - - - - - - - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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