[SPDK] Max Transfer Length
krath at cloudsimple.com
Tue May 2 19:48:53 PDT 2017
Thanks for the info Jim.
> 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.
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