Anyone using iSCSI over DRBD? And a slow internet link perhaps?

If yes, you are likely to see connection errors, host resets, and eventually,
I/O errors reported, for example:

Jan  7 21:47:09 vmware1 kernel:  connection23:0: iscsi: detected conn error 
(1011)
Jan  7 21:47:10 vmware1 kernel: iscsi: host reset succeeded
Jan  7 21:47:50 vmware1 kernel:  connection23:0: iscsi: detected conn error 
(1011)
Jan  7 21:47:50 vmware1 kernel: iscsi: host reset succeeded
Jan  7 21:48:00 vmware1 kernel: sd 22:0:0:1: SCSI error: return code = 
0x00020000
Jan  7 21:48:00 vmware1 kernel: end_request: I/O error, dev sdw, sector 1494720
Jan  7 21:48:00 vmware1 kernel: Buffer I/O error on device sdw, logical block 
186840
Jan  7 21:48:00 vmware1 kernel: lost page write due to I/O error on sdw


This is due to the fact that open-iscsi doesn't seem to like low-speed (but 
stable)
connections to the target.

To reproduce:

1) set up a connection with limited speed between the target and the initiator,
for example, with openvpn, one would use "--shaper 50000" option to limit the 
speed
to 50 kB/s.

2) login the target to the initiator over this connection (can be also in LAN)

3) start reading and writing... after some time you will be seeing connection 
errors and 
host resets followed by I/O errors, possibly data corruption


A harder way to reproduce (but somehow more realistic) would be to set up DRBD,
start background synchronization at high speed (thus leaving not much bandwidth 
for
normal writes), start reading and writing...


I can reproduce it with tgtd and IET, so I guess open-iscsi is to be blamed.

Ideas what's wrong and why it fails?


-- 
Tomasz Chmielewski
http://wpkg.org

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