Messages in this thread | | | Date | Tue, 07 Feb 2012 15:28:54 +0100 | From | Paolo Bonzini <> | Subject | Re: Pe: [PATCH v5 1/3] virtio-scsi: first version |
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On 02/07/2012 02:59 PM, Christian Hoff wrote: > Instead the format has some disadvantages: > - It uses up 8 bytes where 3 bytes would be sufficient in order to store > both the target ID and LUN number information > - The format limits us to 255 target IDs. I agree that the LUN limit is > probably more a theoretical and not a practical one, but 255 target IDs > could become a limitation in the future.
It also provides better upwards-compatibility in case the limitations are actually hit. If I had used "uint8_t target; uint16_t lun;" an extension would require a feature bit and a new struct. With 8-bytes, you can just expand the definition. That pretty much sums it up.
But again, I don't think the limitations are serious. A MegaSAS header has room for 256 targets too, VMWare has only 15, Hyper-V has 1 (and 2 channels, but I think that's an off-by-one), and you can always have multiple HBAs on the same guest.
> Nonetheless I think that virtio-scsi is a useful project and addresses > many of the limitations imposed by virtio-block. The fact that I am still > persisting has more to do with interest in the project rather than wanting > to keep the code from going upstream.
No problem. :)
Paolo
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