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SubjectRe: [PATCH v2 2/2] dm unstripe: Add documentation for unstripe target
On Tue, Dec 12, 2017 at 01:35:13PM +0200, Nikolay Borisov wrote:
> On 11.12.2017 18:00, Scott Bauer wrote:
> > + As an example:
> > +
> > + Intel NVMe drives contain two cores on the physical device.
> > + Each core of the drive has segregated access to its LBA range.
> > + The current LBA model has a RAID 0 128k stripe across the two cores:
> > +
> > + Core 0: Core 1:
> > + __________ __________
> > + | LBA 511| | LBA 768|
> > + | LBA 0 | | LBA 256|
> > + ⎻⎻⎻⎻⎻⎻⎻⎻⎻⎻ ⎻⎻⎻⎻⎻⎻⎻⎻⎻⎻
>
> If it's 128k stripe shouldn't it be LBAs 0/256 on core0 and LBAs 128/511
> on core1?

Ah, this device's makers call the "stripe" size what should be called
"chunk". This device has a 128k chunk per core with two cores, so the
full stripe is 256k. The above should have core 0 owning LBA 512 rather
than 511 (assuming 512b LBA format).

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