On 16 Feb 2009 at 12:36, Mike Christie wrote: > > Ulrich Windl wrote: > > Hi, > > > > my apologies if this was asked and answered before, but I just tried to get > > a > > HOWTO on iSCSI and multipath, but failed to find something really usable. > > > > I have a question regarding various timeouts, specifically (SCSI command, > > TCP > > connection, multipath). Somehow those timeout s are hierarchical, meaning > > the > > multipath daemon (or kernel module) will send some command to a virtual > > SCSI > > device (iSCSI here), then the iSCSI layer will send a TCP packet on the > > wire, and > > after some further unpacking a more or less real SCSI device will receive a > > command. > > > > If I name those timeouts tm (multipath), tt (TCP), and ts (SCSI) > > respectively, > > should the following be true: > > > > tm < tt < ts > > > > Or should the exact opposite be true: > > > > tm > tt > ts > > Are you using dm-multipath? If so what timeout are you referencing? > > I tried to document what I think you are asking in the section 8 of the > README. Does that help?
Hi Mike and others! I'm about examining multipath, and the timeouts were still all default. I was worrying about the timeout for the path checkers: if it takes a minute (just for example) to detect that a path is not usable, I/O might also hang for a minute. Then if the packet to query the multipath status was committed to TCP for transport, and the network had a problem, TCP might be able to recover. So if the timeout for the patch checker is too small (5 seconds, for example), link status may be changed unneccessarily. I'm trying to get my thoughts clear on that. In my version of README (/usr/share/doc/packages/open-iscsi/README of SLES10 SP1), the section 8 is labelled "8. iSCSI System Info", and it doesn't mention timeouts. Regards, Ulrich --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to open-iscsi@googlegroups.com To unsubscribe from this group, send email to open-iscsi+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/open-iscsi -~----------~----~----~----~------~----~------~--~---
