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On Thursday, 2 January 2020 14:43:58 GMT Rich Freeman wrote: |
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> Out of curiosity, what model drive is it? Is it by chance an SMR / |
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> archive drive? |
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Good catch! I hadn't thought of this - the Linux kernel will need to have |
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DM_ZONED enabled I think, for the OS to manager the shingled writes |
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sequentially, but I don't have this enabled here because AFAIK I have no such |
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drives in my possession. |
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> Due to the limitations on how those write data out I |
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> could see them implementing an internal filesystem that journals |
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> incoming data and then writes it back out after the fact. |
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SMR drives which implement a 'device managed' write mechanism, will use their |
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own firmware to control data storage. The OS would not be aware of anything |
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being different to a conventional drive. |
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> If so then |
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> that might happen even after the kernel thinks it is unmounted. |
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> However, such a drive firmware would probably use a journal that |
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> ensures data is safe even if power is cut mid-operation. The drive |
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> isn't supposed to report that a write is completed until it is |
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> durable. |
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Which I take it to mean the drive would not be unmounted by the OS until it is |
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safe to do so and for all intends and purposes it will also be safe to be |
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powered down thereafter. I would think this would be within seconds of |
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successfully unmounting it. Spinning for 30 minutes or more after it is |
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unmounted sounds excessive to me, if it is only being spun by the firmware for |
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flushing its journal buffers. I have a conventional USB drive (WD passport) |
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which is always spinning whether it is being written to or not. |
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-- |
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Regards, |
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Mick |