Flusing caches on shutdown

From: David Balazic (david.balazic@uni-mb.si)
Date: Mon Feb 19 2001 - 07:45:57 EST

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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
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