Messages in this thread | | | Subject | Re: [PATCH 07/14] target/sbc: Add P_TYPE + PROT_EN bits to READ_CAPACITY_16 | From | "Martin K. Petersen" <> | Date | Fri, 10 Jan 2014 15:46:17 -0500 |
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>>>>> "Andy" == Andy Grover <agrover@redhat.com> writes:
Andy> Yes, don't you need FORMAT UNIT because protection information is Andy> going to mean the pi-enabled lun will need to report less blocks?
Modern disk drives won't shrink when you reformat them with PI. This is a result of an IDEMA agreement about LBA counts.
And if you create a 10GB PI LUN on an array you'll get 10GB for data.
Andy> The ramdisk backstore changes in this series allocate extra space Andy> for PI info, but my understanding was that especially for Andy> emulation with block and fileio backstores, everything needs to go Andy> in the same amount of space.
For both file and block I'd recommend we store the PI in a separate block device or file unless the backing device is PI-capable.
Andy> Furthermore, if we want PI info stored along with the blocks, then Andy> block and fileio backstore formats are no longer going to be 1:1 Andy> -- requiring offset calculations, non-aligned read-modify-write, Andy> and all that unpleasantness to be handled?
I only think interleaved makes sense if you're passing the PI through instead of emulating.
-- Martin K. Petersen Oracle Linux Engineering
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