Hello,   This is documented in the Release notes for 7.0.x firmware.  There is a bug in Multipathd, that's exposed with 7.0.x. firmware.   Change readsector0 to TUR or DIRECTIO and restart multipathd.  The protocol errors will stop and Linux MPIO will work fine.   Regards, 
I'm trying to use the regular linux multipath (device-mapper-multipath) with my PS6100 and it's not working at all. It's giving me "readsector0 checker reports path is down", "pdu (op 0x50000370 itt 0x1) rejected. Reason code 0x4" errors and my iSCSI connections are being reset every few seconds. My OS is Oracle Linux 5.10 (fully updated) and my PS6100 is running with the latest firmware 7.0.5. The latest Dell HIT kit for Linux, 1.3.0-2, is working fine on this machine but the reason why I'm trying multipathd is to compare performance between both solution. If we look at other system we have that are running the regular multipathd, the Dell multipath might be giving us slower performance. We doubt it but we want to do the tests and do some performance stats comparison. We have another server that almost has the same configuration (same OS connected to another PS6100) and multipathd is working fine on this one. And one of the difference between this system and the non working one is that the PS6100 is running on firmware 5.2.5 instead of 7.0.5. I would be willing to downgrade the firmware (this unit is not in production yet and I don't mind losing the data on it) but I'm not finding anything on the internet that show how to do it other than "call Dell and they will do it for you". If the only thing you need to do is a special command in the CLI then why there is no documentation on it? So i wonder if someone here is running an equallogic firmware 7.0.5 with the linux multipathd and a RedHat 5 Based OS (CentOS, Oracle Linux, Redhat, etc)?
PS6100 with firmware 7.0.5 + Oracle Linux 5.10 + multipathd issue