Change in vdsm[master]: Rescan FC when rescanning for new multipath devices

smizrahi at redhat.com smizrahi at redhat.com
Sun Oct 27 16:54:17 UTC 2013


Saggi Mizrahi has posted comments on this change.

Change subject: Rescan FC when rescanning for new multipath devices
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Patch Set 5:

(1 comment)

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File vdsm/storage/multipath.py
Line 107:     Should only be called from hsm._rescanDevices()
Line 108:     """
Line 109: 
Line 110:     # First ask fc and iSCSI to rescan all of their sessions
Line 111:     fc.rescan()
As I said "- - -" and issue_lip are two different things. The former is for iscsi the latter is for fc.

Also fc.rescan is completely async so it wouldn't block iscsi rescans.

doing issue_lip will suspend all IO on the HBA since it causes a bus reset. The suspend doesn't effect all IO in the system. Which means that paths that don't use FC are unaffected.

I agree it's problematic but we call multipath.rescan() in only 3 places.

1) sdc.refreshStorage()
2) scanDevicesVisibility
3) formatStorageDomain

In all those cases we do want to be 100% sure that our view of the storage topology is up to date.

We could move to a "rescan on miss" strategy for 2 and 3. I don't know how much getDeviceList() and sdc.refreshStorage() is hammered though.

In any case, I agree that this needs further discussion.
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I disagree with a move to rescan-scsi-bus.sh since it was meant to be used by human administrators and has different priorities and goals from our own. If we keep things in VDSM it'll be much easier to optimize and synchronize when necessary.
Line 112:     iscsi.rescan()
Line 113: 
Line 114:     # Now let multipath daemon pick up new devices
Line 115: 


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Gerrit-MessageType: comment
Gerrit-Change-Id: Idec939222676a24452e8825b36db68839bfd2bbc
Gerrit-PatchSet: 5
Gerrit-Project: vdsm
Gerrit-Branch: master
Gerrit-Owner: Saggi Mizrahi <smizrahi at redhat.com>
Gerrit-Reviewer: Ayal Baron <abaron at redhat.com>
Gerrit-Reviewer: Barak Azulay <bazulay at redhat.com>
Gerrit-Reviewer: Eduardo <ewarszaw at redhat.com>
Gerrit-Reviewer: Federico Simoncelli <fsimonce at redhat.com>
Gerrit-Reviewer: Saggi Mizrahi <smizrahi at redhat.com>
Gerrit-Reviewer: Yaniv Bronhaim <ybronhei at redhat.com>
Gerrit-Reviewer: Yeela Kaplan <ykaplan at redhat.com>
Gerrit-HasComments: Yes


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