number of outstanding FCP transfer ready

Is there a limit to the number of outstanding FCP transfer ready IUs on
a single exchange? If the limit is 1 then is the limited negotiated?

Thanks

On Nov 29, 8:06 am, Granite Park wrote:
Is there a limit to the number of outstanding FCP transfer ready IUs on
a single exchange? If the limit is 1 then is the limited negotiated?

In the case of FCP, the number of outstanding Transfer ready IUs is
one. However, there could be more number of transfer rdy's provided by
the device depending on various conditions of implementation for an I/O
depending on the size of the I/O. In the case of iSCSI,the outstanding
R2Ts which is equivalent to FCP Transfer rdy's is negotiable during the
login phase.

Hope this helps

TK

Thanks

Maybe the number of outstanding transfer ready's is exactly 1 due to the
transfer of sequence initiative to the other side in FCP. I agree
that iSCSI provides a mechanism to negotiate a number 1, and this will
be useful over high latency networks.


On Nov 29, 8:06 am, Granite Park wrote:
Is there a limit to the number of outstanding FCP transfer ready IUs on
a single exchange? If the limit is 1 then is the limited negotiated?

In the case of FCP, the number of outstanding Transfer ready IUs is
one. However, there could be more number of transfer rdy's provided by
the device depending on various conditions of implementation for an I/O
depending on the size of the I/O. In the case of iSCSI,the outstanding
R2Ts which is equivalent to FCP Transfer rdy's is negotiable during the
login phase.

Hope this helps

TK

Thanks

The number of transfer readys are not negotiated. Transfer readys are a bi
product of SCSI WRITE operations. Transfer size is typically bounded by
the capabilities of the o/s kernel and HBA driver combination. Multiple
transfer readys may occur during a single fibre channel exchange.

The Moojit

"Granite Park" wrote in message
news:ceibh.15947$Uz.10868@trnddc05...
Is there a limit to the number of outstanding FCP transfer ready IUs on a
single exchange? If the limit is 1 then is the limited negotiated?

Thanks

Moojit wrote:
The number of transfer readys are not negotiated. Transfer readys are a bi
product of SCSI WRITE operations. Transfer size is typically bounded by
the capabilities of the o/s kernel and HBA driver combination. Multiple
transfer readys may occur during a single fibre channel exchange.

Transfer Ready's are issued by the target not the initiator. They are
therefore
NOT bounded by the OS/kernel or the HBA. Generally, they are bounded by
buffering strategy and available buffer resources in the target. A
useful (but
perhaps not very realistic) example would be to consider a disk drive
with
an 8MB cache. If it write for 16MB is issued to the drive it will have
to break
that write up into 8MB (max) or lesser transfers in order to process
the write
command.

Dave

The Moojit