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一个iSCSI协议实现源代码

The drivers included here are an initial implementation of iSCSI for linux.
This is a quick HOWTO on how to get iSCSI up and running in your environment.

Getting Started

To use these modules you need to have 2 machines running linux 2.4.x connected
together via some TCP/IP network.  (using 1 machine and running both the target
and client on localhost probably works but is untested).

1 machine should have a SCSI adapter installed with a SCSI device (disk)
preferably using SCSI Id 0.  This machine is henceforth referred to as the
"target" machine.  The other machine is henceforth reffered to as the "client"
machine.

*DO NOT USE A TARGET SCSI DEVICE CONTAINING IMPORTANT DATA*
You have been warned.


Installing

-- Client Side --

On the client machine download the initiator source distribution from here:

http://www.cs.uml.edu/~mbrown/iSCSI/iscsi-0.1.tar.gz

Make sure /usr/src/linux contains the source to your running kernel and is
version 2.4.x.  Extract the sources:

   $ tar -zxvf iscsi-0.1.tar.gz
   $ cd iscsi

Edit the file iscsi_client.c.  Change line 488 to:

        u32 addr = <target_ip_address>;

where target_ip_address is the IP address of your target machine in
hex format in network byte ordering.  There are some examples included
there to help.  Build the iscsi and iscsi_client kernel modules:

   $ make

-- Target Side -- 

On the target machine download the target source distribution from here:

ftp://ftp.iol.unh.edu/pub/iscsi/kernel_emulator_10.tgz

Like the client, make sure /usr/src/linux contains the source to your running 
kernel and is version 2.4.x.  Extract the sources:

   $ tar -zxvf kernel_emulator_10.tgz
   $ cd kernel_emulator_10

Edit the file scsi_target.h.  Comment line 47:

//# define MEMORYIO

Uncomment line 49:

#define FILEIO

For an explanation of what these modes of operations do, read Ashish Palekar's
paper included with the distribution (tr0101.pdf).  Currently the client
distribution works with either MEMORYIO or FILEIO.  (Ashish has said
GENERICIO mode works, I have been unable to get it working.  This is sill
being investigated)

Build the iscsi_target and scsi_target kernel modules:

   $ make

Note this distribution also includes a qlogicfc driver and an sep_target
driver.  These are not needed for our purposes.

Optionally instead of using the kernel target, you may use the user space
target provided with the client distribution.  This is currently
undocumented but should be straightforward to use.  It is intended to 
simplify debugging the client for those wishing to hack my client code.

-- Kernel Configuration --

On both machines make sure your kernel has compiled in support or modules for 
scsi, sg, and sd.  (st and sr too if the device you want to use over iscsi 
is a cdrom or tape).  On the target machine make sure you have compiled in
support or modules for your scsi adapter.

-- Running --

Before executing these insmod lines make sure your have the appropriate
scsi modules loaded if necesary.  The target modules when running in FILEIO
mode open up two files scsi_disk_file_0_0 and scsi_disk_file_0_1 in the current
directory.  It uses these files as virtual disks.  Before loading the 
target kernel modules, on the target machine create a symbolic link from
your scsi device to scsi_disk_file_0_0:

(in my case, I have a 520MB scsi disk attached to the only scsi adapter in the machine)

   $ ln -s /dev/sda scsi_disk_file_0_0

1.  On the target, execute:
   $ insmod ./scsi_target.o
   $ insmod ./iscsi_target.o

2.  On the client, execute:
   $ insmod ./iscsi.o
   $ insmod ./iscsi_client.o

Note the target should be up and running before the client modules are loaded,
otherwise the client will cause a kernel panic() due to a bug in my code.
Also note that rmmod'ing the iscsi_client module will cause a panic() due
to a bug in my code.  Suggest rebooting the client for each new instantiation.

-- Using iSCSI --

All commands henceforth are to be executed on the client.  No further
work is required on the target.

Assuming that my directions were accurate and everything went ok, by this 
point you should have a working iSCSI connection.  To verify, machine execute:

   $ lsmod

and verify iscsi and iscsi_client are loaded.

   $ cat /proc/scsi/scsi

and verify you see a listing similar to:

Attached devices: 
Host: scsi0 Channel: 00 Id: 00 Lun: 00
  Vendor: UNH-IOL  Model: Target Emulator  Rev: 1.1 
  Type:   Direct-Access                    ANSI SCSI revision: 01
....

   $ cat /proc/scsi/iscsi_client/0

and verify you see a message similar to:

This driver implements the IETF iSCSI draft (SCSI over TCP/IP)

At this point hopefully you've verified that your iSCSI setup is up and 
running.  If there are no other SCSI adapters on your system, the first device 
available should be /dev/sda.  You may now use /dev/sda on the client like
any other SCSI disk as if it were local to the client.  Examples include:

   ( to view/modify the partition table )
   $ fdisk /dev/sda

   ( to create an ext2 filesystem on the first partition )
   $ mke2fs /dev/sda1

   ( to mount the iscsi partition )
   $ cd /mnt
   $ mkdir iscsi
   $ mount /dev/sda1 /mnt/iscsi -t ext2

   ( to copy files to and from the mounted iscsi partition )
   $ cp /etc/passwd /mnt/iscsi/
   $ cp /boot/vmlinuz-2.4.3 /mnt/iscsi/
   $ cp /mnt/iscsi/passwd /tmp/passwd
   $ cp /mnt/iscsi/vmlinuz-2.4.3 /tmp/vmlinuz-2.4.3

   ( to verify the integrity of the files copied to and from the iscsi
     partition )
   $ diff /tmp/passwd /etc/passwd
   $ diff /tmp/vmlinuz-2.4.3 /boot/vmlinuz-2.4.3

-- Final Notes --

When you are done playing with the iscsi mount you should unmount per 
usual via:
   
   $ umount /mnt/iscsi

In addition, since the client's kernel thinks its the only entity to ever
access that scsi disk it may have buffered mount state.  You should run:

   $ sync

to force the client to flush any and all outstanding kernel buffers.

Performance is abysmal in my setup, 10 Mbit eth network. 
100K/s according to hdparm.  I have a number of theories I am investigating.

-- Problems/Questions/Flames --

Any problems you encounter specifically with the client setup should be
directed to me, Michael F. Brown, [e-mail].  Feel free to also
contact me with help with the target setup.  If I can't answer your questions
about the target, I will forward them to Ashish Palekar, the author of the
target drivers.