RE: [PATCH 3/3 2.6.29] cxgb3i -- documentation

["Karen Xie" <kxie@xxxxxxxxxxx>]

Thanks for the spell check. Will fix them.

Thanks,
Karen

-----Original Message-----
From: Randy Dunlap [mailto:randy.dunlap@xxxxxxxxxx] 
Sent: Sunday, December 14, 2008 4:46 PM
To: Karen Xie
Cc: linux-scsi@xxxxxxxxxxxxxxx; open-iscsi@xxxxxxxxxxxxxxxx;
michaelc@xxxxxxxxxxx; James.Bottomley@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [PATCH 3/3 2.6.29] cxgb3i -- documentation

Karen Xie wrote:
> [PATCH 3/3 2.6.29] cxgb3i -- documentation
> 
> From: Karen Xie <kxie@xxxxxxxxxxx>
> 
> - document cxgb3i driver's capablity and setup steps to be used with
>   open-iscsi initiator.
> 
> Signed-off-by: Karen Xie <kxie@xxxxxxxxxxx>
> ---
> 
>  Documentation/scsi/cxgb3i.txt |   81
+++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 81 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/scsi/cxgb3i.txt
> 
> 
> diff --git a/Documentation/scsi/cxgb3i.txt
b/Documentation/scsi/cxgb3i.txt
> new file mode 100644
> index 0000000..9456013
> --- /dev/null
> +++ b/Documentation/scsi/cxgb3i.txt
> @@ -0,0 +1,81 @@
> +Chelsio S3 iSCSI Driver for Linux
> +
> +Introduction
> +============
> +
> +The Chelsio T3 ASIC based Adapters (S310, S320, S302, S304, Mezz
cards, etc.
> +series of products) supports iSCSI acceleration and iSCSI Direct Data
Placement

                       support

> +(DDP) where the hardware handles the expensive byte touching
operations, such
> +as CRC computation and verification, and direct DMA to the final host
memory
> +destination:
> +
> +	- iSCSI PDU digest generation and verification
> +
> +	  On transmitting, Chelsio S3 h/w computes and inserts the
Header and
> +	  Data digest into the PDUs.
> +	  On receiving, Chelsio S3 h/w computes and verifies the Header
and
> +	  Data digest of the PDUs.
> +
> +	- Direct Data Placement (DDP)
> +
> +	  S3 h/w can directly place the iSCSI Data-In or Data-Out PDU's
> +	  payload into pre-posted final destination host-memory buffers
based
> +	  on the Initiator Task Tag (ITT) in Data-In or Target Task Tag
(TTT)
> +	  in Data-Out PDUs.
> +
> +	- PDU Transmit and Recovery
> +
> +	  On transmitting, S3 h/w accepts the complete PDU (header +
data)
> +	  from the host driver, computes and inserts the digests,
decomposes
> +	  the PDU into multiple TCP segments if necessary, and transmit
all
> +	  the TCP segments onto the wire. It handles TCP retransmission
if
> +	  needed.
> +
> +	  On receving, S3 h/w recovers the iSCSI PDU by reassembling TCP

	     receiving,

> +	  segments, separating the header and data, calculating and
verifying
> +	  the digests, then forwards the header to the host. The payload
data,

	                    forwarding

> +	  if possible, will be directly placed into the pre-posted host
DDP
> +	  buffer. Otherwise, the payload data will be sent to the host
too.
> +
> +The cxgb3i driver interfaces with open-iscsi initiator and provides
the iSCSI
> +acceleration through Chelsio hardware wherever applicable.
> +
> +Using the cxgb3i Driver
> +=======================
> +
> +The following steps need to be taken to accelerates the open-iscsi
initiator:
> +
> +1. Load the cxgb3i driver: "modprobe cxgb3i"
> +
> +   The cxgb3i module registers a new transport class "cxgb3i" with
open-iscsi.
> +
> +   * in the case of recompiling the kernel, the cxgb3i selection is
located at
> +	Device Drivers
> +		SCSI device support --->
> +			[*] SCSI low-level drivers  --->
> +				<M>   Chelsio S3xx iSCSI support
> +
> +2. Create an interface file located under /etc/iscsi/ifaces/ for the
new
> +   transport class "cxgb3i".
> +
> +   The content of the file should be in the following format:
> +	iface.transport_name = cxgb3i
> +	iface.net_ifacename = <ethX>
> +	iface.ipaddress = <iscsi ip address>
> +
> +   * if iface.ipaddress is specified, <iscsi ip address> needs to be
either the
> +	same as the ethX's ip address or an address on the same subnet.
Make
> +	sure the ip address is unique in the network.
> +
> +3. edit /etc/iscsi/iscsid.conf
> +   The default setting for MaxRecvDataSegmentLength (131072) is too
big, search

 
big;

> +   and replace all occurances of "xxx.iscsi.MaxRecvDataSegmentLength"
to be a

                      occurrences

> +   value no bigger than 15872 (for example 8192):
> +
> +	discovery.sendtargets.iscsi.MaxRecvDataSegmentLength = 8192
> +	node.conn[0].iscsi.MaxRecvDataSegmentLength = 8192
> +
> +4. To direct open-iscsi traffic to go through cxgb3i's accelerated
path,
> +   "-I <iface file name>" option needs to be specified with most of
the
> +   iscsiadm command. <iface file name> is the transport interface
file created
> +   in step 2.


HTH.

~Randy

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