It is the SCSI driver stack's responsibility to perform the path selection, which in most cases uses a straightforward round-robin approach. I think the main difference worth highlighting is that of the DS6000 path selection, which tries to respect the PREFerred/NOTPREFerred settings in the EDEVice command/statement.
Eric Farman z/VM I/O Development "Romanowski, John (OFT)" <[EMAIL PROTECTED]> Sent by: Linux on 390 Port <[email protected]> 03/08/2006 03:11 PM Please respond to Linux on 390 Port <[email protected]> To [email protected] cc Subject Re: VM I/O load balancing on emulated FBA EDEVICE My understanding of it is FCP channels aren't part of the traditional CCW-based channel subsystem and don't necessarily have their features, such as the channel subsystem picking a path. I suspect CP's FBA emulator or CP's scsi driver stack has to do the I/O load balancing. But I don't know that they do; maybe they just do fail-over if the active path goes down; and all I/O goes down one FCP path. -------------------------------------------------------- This e-mail, including any attachments, may be confidential, privileged or otherwise legally protected. It is intended only for the addressee. If you received this e-mail in error or from someone who was not authorized to send it to you, do not disseminate, copy or otherwise use this e-mail or its attachments. Please notify the sender immediately by reply e-mail and delete the e-mail from your system. -----Original Message----- From: Linux on 390 Port [mailto:[EMAIL PROTECTED] On Behalf Of Michael A. Short Sent: Wednesday, March 08, 2006 2:46 PM To: [email protected] Subject: Re: VM I/O load balancing on emulated FBA EDEVICE I don't think CP is involved in this; this should be the function of the channel subsystem. CP starts a subchannel and subsystem picks an available path. -------------- Original message ---------------------- From: "Romanowski, John (OFT)" <[EMAIL PROTECTED]> > On z/VM5.2 I have an EDEVICE defined with multiple FCP paths to its scsi > device. > Does anyone know if VM does I/O load balancing across the EDEVICE's FCP > paths? > Or does VM use the extra paths just for fail-over when one of the FCP > paths is lost? > -------------------------------------------------------- > This e-mail, including any attachments, may be confidential, privileged or > otherwise legally protected. It is intended only for the addressee. If you > received this e-mail in error or from someone who was not authorized to send it > to you, do not disseminate, copy or otherwise use this e-mail or its > attachments. Please notify the sender immediately by reply e-mail and delete > the e-mail from your system. > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
