On Jul 16, 2007, at 6:06 PM, Torrey McMahon wrote:
Darren Dunham wrote:If it helps at all. We're having a similar problem. Any LUN'sconfigured with their default owner to be SP B, don't get along with ZFS. We're running on a T2000, With Emulex cards and the ssd driver.MPXIO seems to work well for most cases, but the SAN guys are not comfortable with it.Are you using the top level powerpath device? Is the clariion in anauto-trespass mode where any i/o going down the alt path will cause theLUNs to move?My previous experience with powerpath was that it rode below the Solarisdevice layer. So you couldn't cause trespass by using the "wrong" device. It would just go to powerpath which would choose the link to use on its own. Is this not true or has it changed over time?
I haven't looked at power path for some time but it used to be theopposite. The powerpath node sat on top of the actual device paths. One of the selling points of mpxio is that it doesn't have that problem. (At least for devices it supports.) Most of the multipath software had thatsame limitation
I agree, it's not true. I don't know how long it hasn't been true, but the last year and a half I've been implementing PowerPath on Solaris 8, 9, 10, the way to make it work is to point whatever disk tool you're using to the emcpower device. The other paths are there because leadville finds them and creates them (if you're using leadville), but PowerPath isn't doing anything to make them redundant, it's giving you the emcpower device and the emcp, etc. drivers to front end them and give you a multipathed device (the emcpower device). It DOES choose which one to use, for all I/O going through the emcpower device. In a situation where you lose paths and I/O is moving, you'll see scsi errors down one path, then the next, then the next, as PowerPath gets fed the scsi error and tries the next device path. If you use those actual device paths, you're not actually getting a device that PowerPath is multipathing for you (i.e. it does not dig in beneath the scsi driver)
I haven't had any problem making Veritas, Disksuite, or in a very few cases so far ZFS work by pointing them at the emcpower devices. (note that 'not having any problem' included reading the PowerPath manuals and docs before implementing it to make sure it's being done 'right' according to EMC's procedures, not just Sun's or Veritas') I haven't disected
cheers, Brian
However, I'm not an expert on powerpath by any stretch of the imagination. I just took a quick look at the powerpath manual (4.0 version.) and it says you can now use both types which seems a little confusing. Again, I's be interested to see if using the pseudo-deviceworks better.....not to mention how it works using the direct path diskentry.
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