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On Sat, Jun 6, 2020 at 9:57 AM antlists <antlists@××××××××××××.uk> wrote: |
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> |
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> Oh - the other thing - if it's PMR and you're copying files onto it, |
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> expect a puke! That thing on WD Reds going PMR, I copied most of that on |
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> to the linux raid mailing list and the general feeling I get is "PMR is |
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> bad". |
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> |
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You're mixing up PMR/SMR there. PMR=CMR=the way things have been for |
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the last few decades. SMR is the new shingled technology. |
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There is nothing wrong with it per se, but it is NOT a drop-in |
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substitute for all applications. It works best if it is host-managed |
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with a filesystem or application that was engineered specifically to |
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use it. |
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If you tried to swap a hard drive with a tape drive you'd have |
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terrible results 99% of the time, but that doesn't make tape drives a |
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bad thing. They just aren't drop-in substitutes for hard drives and |
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you need to use them with appropriate applications. |
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One of the problems with drive-managed SMR is that it can seem to be |
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ok when you're just doing light duty access, and then when one of your |
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other drives fails and you're doing a zfs resilver the SMR drive |
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starts performing an order of magnitude or more worse and you find |
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yourself painted in to a corner. |
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-- |
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Rich |
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