[SPDK] Max Transfer Length

Kumaraparameshwaran Rathnavel krath at cloudsimple.com
Tue May 2 19:48:53 PDT 2017


Thanks for the info Jim.

Thanking you,
Param

> On 02-May-2017, at 11:47 PM, Harris, James R <james.r.harris at intel.com> wrote:
> 
> 
>> On May 2, 2017, at 1:52 AM, Kumaraparameshwaran Rathnavel <krath at cloudsimple.com> wrote:
>> 
>> Hi All,
>> 
>> Is it possible to change the Transfer size of the iSCSI initiator and target to a configurable value. Right now MAXRECVDATASEGMENTLENGTH is 65536. If I change this to 4096, I still see the initiator requesting more than 4k. Is there any other parameters that i should change at the target level to get read and write requests exactly of the Block size and the Block size that I use is 4096.
> 
> Hi Param,
> 
> MaxRecvSegmentLength only limits the maximum size of iSCSI PDUs - it does not limit the size of SCSI I/O commands.  So limiting MaxRecvSegmentLength to 4KB just means that the data for a 1MB SCSI I/O will basically have to be sent as a sequence of 256 4KB Data PDUs.
> 
> Note also that this value is negotiated twice - once for the maximum length that the target can send to the initiator, and another for the maximum length then initiator can send to the target.
> 
> If you want to artificially limit the maximum size of I/O sent by a Linux iSCSI initiator for testing purposes, you can modify /sys/block/sdX/queue/max_sectors_kb.
> 
> -Jim
> 
> _______________________________________________
> SPDK mailing list
> SPDK at lists.01.org
> https://lists.01.org/mailman/listinfo/spdk


More information about the SPDK mailing list