Messages in this thread | | | From | "Mudama, Eric" <> | Subject | RE: questions regarding Journalling-FSes and w-cache reordering | Date | Wed, 9 Apr 2003 13:52:44 -0600 |
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> -----Original Message----- > > Is a ATA-harddisk allowed to reorder the operations from in > w-cache ?
ATA hard drives are allowed to reorder/merge/etc their write caches if write cache is enabled. With write caching enabled, there is no guarantee that dirty data will be flushed in any specific order, nor does the ATA protocol support any such ordering beyond the global flush cache command.
No order preference is supported in TCQ either except for the optional FUA extensions for ATA-7.
There is nothing in the ATA specification that guarantees data integrity at any given instant in time on the media without a flush cache. (e.g. I am in the process of writing data A, and data B is an arriving overlapping write splice, what do I actually put on the media and in what order)
Power cycling a dirty, busy drive, especially in the middle of error recovery/reallocation, is always a dangerous proposition.
--eric
-- Eric Mudama Maxtor Corporation eric_mudama@maxtor.com 2452 Clover Basin Drive - BC163 303.682.4758 (x4758) Longmont, CO 80503 cell: 303.478.3180
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