On May 7, 2015, at 7:06 AM, Ancoron Luciferis 
<[email protected]> wrote:

> Hi,
> 
> I currently have some trouble with LUNs exposed by Synology boxes.
> 
> As of Linux kernel 3.19, the max_sectors_kb value always is 32767 for
> any LUN, which results into errors on the Synology target side and
> reconnects on the Linux initiator side:
> 


As you saw, in the newer kernel the block/scsi layer will now send requests up 
to the size the target or initiator say they can handle. In your case, because 
the target is reporting zeros, the scsi layer is only using the initiator limit 
which is that 32K.

It seems there is a bug with lio based targets. In this patch for Qnap targets 
which used lio, we just added a new black list flag so we use the old default 
value because we could not contact the vendor to get more info as it is not 
always as simple as just matching the max_hw_sectors/max_sectors on the target 
side:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/scsi?id=35e9a9f93994d7f7d12afa41169c7ba05513721b

You can normally manually override the max sectors setting, but that is broken 
under some conditions. It is fixed with this patch

http://marc.info/?l=linux-scsi&m=142864974021809&w=3

Could you send me the vendor/product info, so we can add your target to the 
blacklist?

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