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IO stops for 45+ seconds when 1 of 4 paths is lost/removed
My hosts are on dual redundant fabrics. Each fabric has a zone that contains the host HBA and 2 ports on the storage system (VPLEX or VNX in this case).
I’ve tried this on many different host configurations but most are Server 2008 R2 w/ native MPIO enabled and set to Round Robin. I have PowerPath VE on a test host. I also have some linux hosts running multipathd. For the purposes of this exercise the results are always the same.
Here’s what the zones look like (simplified)
Fabric A
Host HBA1
Storage1
Storage2
Fabric B
Host HBA2
Storage1
Storage2
I have a situation where I need to change some of the zoning. Ultimately I need to remove “Storage2” from each zone and replace it with “Storage3”
First step I took was to remove “Storage2” and enable the zone config on a single fabric. So we look like this;
Fabric A
Host HBA1
Storage1
Storage2
Fabric B
Host HBA2
Storage1
We’ve gone from 4 paths to 3. While this change took place I had iometer running on the host. When the config was applied IO paused at 0 for 45~47 seconds. Would anyone else expect this behaviour? I expected a small hiccup but not a complete 45+ second outage when losing a single path, when 3 other paths are active and healthy.
Thoughts? Ideas? Considerations? All help is appreciated. EMC support has not been much help with this.
Allen Ward
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April 16th, 2013 08:00
The first place I would look would be at which Storage ports each of the HBAs are going to. I would also look at the initiator settings on the array - in this case specifically the failover mode - to make sure it is configured properly for the host configuration.
For the array ports, I would want to see that each HBAis configured to see one port on each of the two SPs on the array. If each HBA only sees ports on one SP and the failover mode isn't set properly, I can see how this might occur.
AaronAnderson1
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April 16th, 2013 08:00
Everything I've tested thus far has been HOST -> VPLEX. (Except one host in another data center where we don't have a VPLEX)
What in particular would you look for?
Allen Ward
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April 16th, 2013 08:00
Well, I think I'm going to have to let someone else jump in here since you have VPLEX in between. I wasn't clear on that from your first note. I have no VPLEX experience yet, so I'd rather not guess.