On 05/15/2015 06:54 PM, Michael Christie wrote:
>
> On May 7, 2015, at 7:06 AM, Ancoron Luciferis
> <ancoron.lucife...@googlemail.com> 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?
>
Hi,
thanx for the info. I currently have the following devices at my
disposal for testing:
* Synology DS409+
* Synology DS1813+
* Synology DS1815+
All LUNs created on these devices are identified by the following strings:
Vendor: SYNOLOGY
Product: iSCSI Storage
Revision: 3.1
As there is no reliable way to differentiate the block-level from the
file-level LUNs on the initiator side (at least I can't see any reliable
difference in device identification data), setting max_sectors_kb to 512
should be a safe value for Synology LUNs (1024 is too much for its
block-level LUNs).
If you'd like me to collect some more data, please say so.
Cheers,
Ancoron
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