[Stgt-devel] iSER

Robin Humble robin.humble+stgt
Mon Sep 3 15:23:26 CEST 2007


an iSER implementation is pretty exciting - thanks for all your
hard work!

I've been trying out git://git.osc.edu/tgt but I seem to have hit a
problem with larger i/o :-/ hopefully I'm just doing something silly as
I'm fairly new to iSCSI and even newer to tgtd.

so I can connect to an iSCSI/iSER target and small dd's to the device
work eg.
 # dd if=/dev/zero of=/dev/sdc bs=1M count=10
 10+0 records in
 10+0 records out
 10485760 bytes (10 MB) copied, 0.020379 seconds, 515 MB/s

however a slightly larger dd
  # dd if=/dev/zero of=/dev/sdc bs=1M count=100
hits troubles (it appears to eventually complete, albeit with speeds in
the kB/s range) and the iSCSI device is usually left in a non-working
state afterwards eg. "fdisk -l <device>" gives no output.

logs from tgtd -d 9 and from the initiator side are attached.

there are ~millions of these:
 tgtd: iscsi_iser_write_begin(1014) Unable to find send slot
 [iSER]:in iscsi_iser_write_begin nbytes 48.
at the end of the tgtd logs, so for brevity I truncated the file after
a few 100 of them.

dd works as expected when I use TCP or IPoIB instead of iSER.
I tried tgtd in iSER mode with both standard centos5 kernels and ofed
(1.1) and also + ofed1.2. logs are from the latter.

if it matters:
the backing store for the iSER target is a file in a 7.1g ramfs.
the client is booted into a kernel with mem=512M.
centos5, x86_64, dual dual-core Xeon 5150.

target/server setup is:
 mount -t ramfs none -o rw,size=7100M,mode=755 /mnt/ramdisk
 dd if=/dev/zero of=/mnt/ramdisk/file bs=1M count=7000
 modprobe ib_iser
 tgtadm --lld iscsi --mode target --op new --tid 1 --targetname yo
 tgtadm --lld iscsi --mode target --op bind --tid 1 --initiator-address ALL
 tgtadm --lld iscsi --mode target --op update --tid 1 --name MaxRecvDataSegmentLength --value 262144
 tgtadm --lld iscsi --mode target --op update --tid 1 --name FirstBurstLength --value 262144
 tgtadm --lld iscsi --mode logicalunit --op new --tid 1 --lun 1 --backing-store /mnt/ramdisk/file

initiator/client setup is:
   node.startup = manual
   node.session.timeo.replacement_timeout = 120
   node.conn[0].timeo.login_timeout = 15
   node.conn[0].timeo.logout_timeout = 15
   node.conn[0].timeo.noop_out_interval = 10
   node.conn[0].timeo.noop_out_timeout = 15
   node.session.iscsi.InitialR2T = No
   node.session.iscsi.ImmediateData = Yes
   node.conn[0].iscsi.HeaderDigest = None
   node.conn[0].iscsi.DataDigest = None

 modprobe ib_iser
 /etc/init.d/iscsid start
 iscsiadm --mode discovery --type sendtargets --portal $ip
 iscsiadm --mode node --targetname yo --portal $ip:3260 --op update -n node.transport_name -v iser
 iscsiadm --mode node --targetname yo --portal $ip:3260 --login

please let me know if you'd like more info or for me to try
something else out.

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