Bart Van Assche schrieb:
> On Fri, Jan 9, 2009 at 3:22 PM, Tomasz Chmielewski <man...@wpkg.org> wrote:
>> Bart Van Assche schrieb:
>>> # ping -q -i 0.01 -c1000 -s160 ${remote_ip}
>> I get about 1% losses.
>
> IMHO running iSCSI over a slow link should work, but a packet loss of
> 1% is troublesome. On a local network the packet loss rate is about
> 0.001% (1e-5) for 1000-byte packets.
It's not really running iSCSI over a slow link in this case.
DRBD synchronizes two block devices, over a slow link in this case:
P - primary node, accessed by the target, accessed by the initiator
S - secondary node / synchronized area
U - unsynchronized area
PPPPPPPPPPPPPPPPPPPPPPP
<slow link>
SSSUUUUUUUUUUUUUUUUUUUU
Slow link is used to transfer data for unsynchronized area.
Now, if the initiator begins to write data, DRBD has to transfer it to
the secondary node before the write is completed: "writes" flow over a
slow link and compete with background synchronization in the meantime.
As a result, we can say that iSCSI is running over a slow link.
Mike's suggestion help though - increasing timeouts and decreasing the
number of outstanding commands help here.
One more note - I see such connection/host resets from time to time also
when using a gigabit ethernet and a very loaded target (no I/O errors
though, everything recovers on time with the default values).
--
Tomasz Chmielewski
http://wpkg.org
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