| Summary: | scanning storage interconnects and multipath | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 7 | Reporter: | Gopinath Marappan <marappan_gopinath> |
| Component: | doc-Storage_Administration_Guide | Assignee: | Marek Suchánek <msuchane> |
| Status: | CLOSED INSUFFICIENT_DATA | QA Contact: | ecs-bugs |
| Severity: | unspecified | Docs Contact: | |
| Priority: | high | ||
| Version: | 7.0 | CC: | adstrong, marappan_gopinath, revers, rhel-docs |
| Target Milestone: | rc | Keywords: | Documentation |
| Target Release: | --- | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2017-10-17 16:37:51 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
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Description
Gopinath Marappan
2016-10-25 16:36:54 UTC
Specifically we want to know if the following command will require the IOs to be paused in both scenarios - without and with dm-multipath active. echo "- - -" > /sys/class/scsi_host/hosth/scan Reassigning to correct doc component for this manual. Hello, I'm with the docs team and I've asked a Red Hat subject matter expert to respond to your questions. I'll update the Red Hat Enterprise Linux 7 Storage Administration Guide based on the response from the subject matter expert. Thank you. (In reply to Milan Navratil from comment #5) > Hello, > > I'm with the docs team and I've asked a Red Hat subject matter expert to > respond to your questions. > > I'll update the Red Hat Enterprise Linux 7 Storage Administration Guide > based on the response from the subject matter expert. > > Thank you. Due to the unpredictablity in behavior, Red Hat will still recommend against doing rescan during active IO. We could discuss changing this to reflect that Red Hat is deferring to array vendors for such support if EMC is willing to qualify this. Rob (In reply to Rob Evers from comment #6) > (In reply to Milan Navratil from comment #5) > > Hello, > > > > I'm with the docs team and I've asked a Red Hat subject matter expert to > > respond to your questions. > > > > I'll update the Red Hat Enterprise Linux 7 Storage Administration Guide > > based on the response from the subject matter expert. > > > > Thank you. > > Due to the unpredictablity in behavior, Red Hat will still recommend against > doing rescan during active IO. > > We could discuss changing this to reflect that Red Hat is deferring to array > vendors for such support if EMC is willing to qualify this. > > Rob I found another RedHat link that suggests that scanning the bus is okay even without pausing the IOs. https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Online_Storage_Reconfiguration_Guide/adding_storage-device-or-path.html In the link above, the command suggested to scan the bus is: # echo "c t l" > /sys/class/scsi_host/hosth/scan If this command is okay, is the following command also okay to do without pausing the IOs: # echo "- - -" > /sys/class/scsi_host/hosth/scan (In reply to Gopinath Marappan from comment #7) > (In reply to Rob Evers from comment #6) > > (In reply to Milan Navratil from comment #5) > > > Hello, > > > > > > I'm with the docs team and I've asked a Red Hat subject matter expert to > > > respond to your questions. > > > > > > I'll update the Red Hat Enterprise Linux 7 Storage Administration Guide > > > based on the response from the subject matter expert. > > > > > > Thank you. > > > > Due to the unpredictablity in behavior, Red Hat will still recommend against > > doing rescan during active IO. > > > > We could discuss changing this to reflect that Red Hat is deferring to array > > vendors for such support if EMC is willing to qualify this. > > > > Rob > > > I found another RedHat link that suggests that scanning the bus is okay even > without pausing the IOs. > > https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/ > html/Online_Storage_Reconfiguration_Guide/adding_storage-device-or-path.html > > In the link above, the command suggested to scan the bus is: > # echo "c t l" > /sys/class/scsi_host/hosth/scan > > If this command is okay, is the following command also okay to do without > pausing the IOs: > # echo "- - -" > /sys/class/scsi_host/hosth/scan We want to stay with what I said in comment 7. Hi Gopinath, Is EMC willing to qualify dynamic scanning under load and provide documentation indicating support? Rob We are running tests along with PowerPath to qualify this scenario. Will update as soon as they are done. Hello Gopinath, I'm Marek, the new Storage Administration Guide maintainer, taking over from Milan, who discussed this bug with you earlier. Is there any update on the tests? Thanks, Marek We did some tests and did not notice any issues. However, we cannot be sure that there wont be any issues in all scenarios, especially high IO load scenarios. Thanks, Gopi Hello again Gopi, Is it OK for me to close this bug then? Or would you like to keep it open for more research on the topic? Thanks, Marek HI Marek, You may close the ticket. Thanks, Gopi Closing this bug as INSUFFICIENT_DATA for lack of a better description. Gopi, thanks for your help, and have a nice day, Marek |