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Re: [dm-devel] How to config dm-multipath to change a path only if it fails



Hi Flavio,

Since you are using LSI's (I think it is not IBM's :) rdac driver, which
do provide multipathing functionality (as you see only one device per
lun) why do you want to use dm-multipath ?

>From your explanation it looks like you want to use mirroring on top of
the multipathed storage (but you are trying to use multipath) ?! correct
me if I am wrong.

Following are based on my understanding as explained above :)

BTW, dm-multipath will change the path group only when all the paths in
a path group fails. And, as soon as a path in the higher priority path
group comes back up (path checker returns success), dm-multipath will
start sending I/Os on that path.

Looks like changing the "secondary=read-only" to primary=read-write is
not getting reflected in your prio callout functionality.

Since your path checker (tur) returns success for the path with higher
priority, mutipathd daemon reinstates that path, and since the path
priority of that group is higher than the other one, it is made the
active one, and  i/os are sent on that path, which fails and that leads
to failing the path... but.... (goto the start of this paragraph :)


On Fri, 2009-04-24 at 20:47 -0300, Flavio Junior wrote:
> Hi folks, good evening.
> 
> My idea is set dm-multipath to only change from a path if it fails.
> How can I do that?
> 
> Setup is something as:
> 
> - 2x DS4700 IBM Storages
> - 4x Fiber Switches (2 for each storage)
> - 4x Path to each LUN (2 controllers x 2 switches) - But it shows to
> me as a single device, because I'm using IBM rdac driver too.
> 
> Now, I've a primary storage as read-write AND a secundary mirrored
> (bit by bit synchronous) as read-only. Of course, the LUN id's at each
> storage are different so comes my first "hack" using getuid_callout to
> group paths, and prio_callout to set priority higher for primary
> storage and lower for secundary one.
> 
> Everything is working like a charm, configured as:
> 
> Link: http://pastebin.com/f4de2f7ca
> 
> # multipath.conf
> defaults {
>         user_friendly_names     yes
>         path_grouping_policy    failover
>         path_checker            tur
>         hardware_handler        "rdac"
> #       getuid_callout          "/sbin/scsi_id -g -u -s /block/%n"
>         getuid_callout          "/etc/multipath/get_lun_path.sh %n"
> #       prio_callout            /bin/true
>         prio_callout            "/bin/bash
> /etc/multipath/get_lun_path.sh %n prio"
>         failback                8
> }
> 
> devices {
>         device {
>                 vendor       "dummy"
>                 product      "dummy"
>                 prio_callout "/sbin/scsi_id"
>         }
> }
> 
> [root pinky ~]# cat /etc/multipath/get_lun_path.sh
> #!/bin/bash
> 
> DEVICE="$(/sbin/scsi_id -g -u -s /block/$1)"
> SCSI_ID_TABLE="/etc/multipath/scsi_id_multipath"
> 
> if [ $# -lt 1 ]; then
>         exit 1
> fi
> 
> if [ "$2" == "prio" ]; then
>         while read SCSI_ID WWID PRIO; do [ "$SCSI_ID" == "${DEVICE}" ]
> && echo $PRIO; done < $SCSI_ID_TABLE
>         exit 0
> else
>         while read SCSI_ID WWID PRIO; do [ "$SCSI_ID" == "${DEVICE}" ]
> && echo $WWID; done < $SCSI_ID_TABLE
>         exit 0
> fi
> 
> [root pinky ~]# cat /etc/multipath/scsi_id_multipath
> 3600a0b800048834e0000150149dcc594       HomeMaildir1            2
> 3600a0b80004884c4000016e649dcc5a5       HomeMaildir2            2
> 3600a0b80004884c4000016e449dcc534       WebPages                2
> 3600a0b800048834e000014ff49dcc51b       MailQuorumDisk          2
> 3600a0b800048834e0000172c49e76cbb       FileSystemDLM           2
> 3600a0b80004885b40000b78f49dcd7f8       MailQuorumDisk          1
> 3600a0b80004885b40000b79149dcd817       HomeMaildir1            1
> 3600a0b80004885a00000c13349dcd9e5       HomeMaildir2            1
> 3600a0b80004885b40000baa149ec46b5       FileSystemDLM           1
> 3600a0b80004885a00000c13149dcd9c3       WebPages                1
> 
> [root pinky ~]# multipath -ll
> fs_dlm0 (FileSystemDLM) dm-8 IBM,VirtualDisk
> [size=300M][features=0][hwhandler=0][rw]
> \_ round-robin 0 [prio=2][active]
>  \_ 3:0:0:4 sdf 8:80  [active][ready]
> \_ round-robin 0 [prio=1][enabled]
>  \_ 3:0:1:3 sdj 8:144 [active][ready]
> homemaildir1 (HomeMaildir2) dm-5 IBM,VirtualDisk
> [size=25G][features=0][hwhandler=0][rw]
> \_ round-robin 0 [prio=2][active]
>  \_ 3:0:0:1 sdc 8:32  [active][ready]
> \_ round-robin 0 [prio=1][enabled]
>  \_ 3:0:1:2 sdi 8:128 [active][ready]
> webpages0 (WebPages) dm-6 IBM,VirtualDisk
> [size=4.0G][features=0][hwhandler=0][rw]
> \_ round-robin 0 [prio=2][active]
>  \_ 3:0:0:2 sdd 8:48  [active][ready]
> \_ round-robin 0 [prio=1][enabled]
>  \_ 3:0:1:4 sdk 8:160 [active][ready]
> homemaildir0 (HomeMaildir1) dm-4 IBM,VirtualDisk
> [size=25G][features=0][hwhandler=0][rw]
> \_ round-robin 0 [prio=2][active]
>  \_ 3:0:0:0 sdb 8:16  [active][ready]
> \_ round-robin 0 [prio=1][enabled]
>  \_ 3:0:1:1 sdh 8:112 [active][ready]
> qdisk0 (MailQuorumDisk) dm-7 IBM,VirtualDisk
> [size=200M][features=0][hwhandler=0][rw]
> \_ round-robin 0 [prio=2][active]
>  \_ 3:0:0:3 sde 8:64  [active][ready]
> \_ round-robin 0 [prio=1][enabled]
>  \_ 3:0:1:0 sdg 8:96  [active][ready]
> 
> #####
> 
> The problem comes when my higher priority path goes down (it happens
> if I change secundary=read-only storage role to primary=read-write),
> so dm-multipath fail to secundary path but it keeps trying to change
> back for my "primary" path, and fill /var/log/messages with it (is at
> last of above post link):
> 
> Apr 24 20:26:52 cerebro multipathd: homemaildir0: switch to path group #2
> Apr 24 20:26:53 cerebro kernel: 91
> [RAIDarray.mpp]IBM_DS4700_SITE1:1:0:0 Unrecognized SK - 7
> Apr 24 20:26:53 cerebro kernel: 492
> [RAIDarray.mpp]IBM_DS4700_SITE1:1:0:0 IO FAILURE. vcmnd SN 20095 pdev
> H1:C0:T1:L0 0x07/0x27/0x00 0x08000002 mpp_status:1
> Apr 24 20:26:53 cerebro kernel: sd 3:0:1:0: SCSI error: return code = 0x08000002
> Apr 24 20:26:53 cerebro kernel: sdg: Current: sense key: Data Protect
> Apr 24 20:26:53 cerebro kernel:     Add. Sense: Write protected
> Apr 24 20:26:53 cerebro kernel:
> Apr 24 20:26:53 cerebro kernel: end_request: I/O error, dev sdg, sector 1289
> Apr 24 20:26:53 cerebro kernel: device-mapper: multipath: Failing path 8:96.
> Apr 24 20:26:53 cerebro multipathd: dm-5: add map (uevent)
> Apr 24 20:26:53 cerebro multipathd: dm-5: devmap already registered
> Apr 24 20:26:58 cerebro multipathd: 8:96: mark as failed
> Apr 24 20:26:58 cerebro multipathd: homemaildir0: remaining active paths: 1
> Apr 24 20:26:58 cerebro multipathd: sdg: tur checker reports path is up
> Apr 24 20:26:58 cerebro multipathd: 8:96: reinstated
> Apr 24 20:26:58 cerebro multipathd: homemaildir0: remaining active paths: 2
> Apr 24 20:26:58 cerebro multipathd: dm-5: add map (uevent)
> Apr 24 20:26:58 cerebro multipathd: dm-5: devmap already registered
> Apr 24 20:27:06 cerebro multipathd: homemaildir0: switch to path group #2
> Apr 24 20:27:07 cerebro kernel: 91
> [RAIDarray.mpp]IBM_DS4700_SITE1:1:0:0 Unrecognized SK - 7
> Apr 24 20:27:07 cerebro kernel: 492
> [RAIDarray.mpp]IBM_DS4700_SITE1:1:0:0 IO FAILURE. vcmnd SN 20212 pdev
> H1:C0:T1:L0 0x07/0x27/0x00 0x08000002 mpp_status:1
> Apr 24 20:27:07 cerebro kernel: sd 3:0:1:0: SCSI error: return code = 0x08000002
> Apr 24 20:27:07 cerebro kernel: sdg: Current: sense key: Data Protect
> Apr 24 20:27:07 cerebro kernel:     Add. Sense: Write protected
> Apr 24 20:27:07 cerebro kernel:
> Apr 24 20:27:07 cerebro kernel: end_request: I/O error, dev sdg, sector 1289
> Apr 24 20:27:07 cerebro kernel: device-mapper: multipath: Failing path 8:96.
> Apr 24 20:27:07 cerebro multipathd: dm-5: add map (uevent)
> Apr 24 20:27:07 cerebro multipathd: dm-5: devmap already registered
> Apr 24 20:27:07 cerebro multipathd: 8:96: mark as failed
> Apr 24 20:27:07 cerebro multipathd: homemaildir0: remaining active paths: 1
> Apr 24 20:27:12 cerebro multipathd: sdg: tur checker reports path is up
> Apr 24 20:27:12 cerebro multipathd: 8:96: reinstated
> Apr 24 20:27:12 cerebro multipathd: homemaildir0: remaining active paths: 2
> Apr 24 20:27:12 cerebro multipathd: dm-5: add map (uevent)
> Apr 24 20:27:12 cerebro multipathd: dm-5: devmap already registered
> Apr 24 20:27:20 cerebro multipathd: homemaildir0: switch to path group #2
> Apr 24 20:27:21 cerebro kernel: 91
> [RAIDarray.mpp]IBM_DS4700_SITE1:1:0:0 Unrecognized SK - 7
> Apr 24 20:27:21 cerebro kernel: 492
> [RAIDarray.mpp]IBM_DS4700_SITE1:1:0:0 IO FAILURE. vcmnd SN 20305 pdev
> H1:C0:T1:L0 0x07/0x27/0x00 0x08000002 mpp_status:1
> Apr 24 20:27:21 cerebro kernel: sd 3:0:1:0: SCSI error: return code = 0x08000002
> Apr 24 20:27:21 cerebro kernel: sdg: Current: sense key: Data Protect
> Apr 24 20:27:21 cerebro kernel:     Add. Sense: Write protected
> Apr 24 20:27:21 cerebro kernel:
> Apr 24 20:27:21 cerebro kernel: end_request: I/O error, dev sdg, sector 1289
> Apr 24 20:27:21 cerebro kernel: device-mapper: multipath: Failing path 8:96.
> Apr 24 20:27:21 cerebro multipathd: dm-5: add map (uevent)
> Apr 24 20:27:21 cerebro multipathd: dm-5: devmap already registered
> Apr 24 20:27:21 cerebro multipathd: 8:96: mark as failed
> Apr 24 20:27:21 cerebro multipathd: homemaildir0: remaining active paths: 1
> Apr 24 20:27:26 cerebro multipathd: sdg: tur checker reports path is up
> Apr 24 20:27:26 cerebro multipathd: 8:96: reinstated
> Apr 24 20:27:26 cerebro multipathd: homemaildir0: remaining active paths: 2
> Apr 24 20:27:26 cerebro multipathd: dm-5: add map (uevent)
> Apr 24 20:27:26 cerebro multipathd: dm-5: devmap already registered
> Apr 24 20:27:34 cerebro multipathd: homemaildir0: switch to path group #2
> Apr 24 20:27:35 cerebro kernel: 91
> [RAIDarray.mpp]IBM_DS4700_SITE1:1:0:0 Unrecognized SK - 7
> Apr 24 20:27:35 cerebro kernel: 492
> [RAIDarray.mpp]IBM_DS4700_SITE1:1:0:0 IO FAILURE. vcmnd SN 20419 pdev
> H1:C0:T1:L0 0x07/0x27/0x00 0x08000002 mpp_status:1
> Apr 24 20:27:35 cerebro kernel: sd 3:0:1:0: SCSI error: return code = 0x08000002
> Apr 24 20:27:35 cerebro kernel: sdg: Current: sense key: Data Protect
> Apr 24 20:27:35 cerebro kernel:     Add. Sense: Write protected
> Apr 24 20:27:35 cerebro kernel:
> Apr 24 20:27:35 cerebro kernel: end_request: I/O error, dev sdg, sector 1289
> Apr 24 20:27:35 cerebro kernel: device-mapper: multipath: Failing path 8:96.
> Apr 24 20:27:35 cerebro multipathd: dm-5: add map (uevent)
> Apr 24 20:27:35 cerebro multipathd: dm-5: devmap already registered
> Apr 24 20:27:35 cerebro multipathd: 8:96: mark as failed
> Apr 24 20:27:35 cerebro multipathd: homemaildir0: remaining active paths: 1
> Apr 24 20:27:40 cerebro multipathd: sdg: tur checker reports path is up
> Apr 24 20:27:40 cerebro multipathd: 8:96: reinstated
> Apr 24 20:27:40 cerebro multipathd: homemaildir0: remaining active paths: 2
> Apr 24 20:27:40 cerebro multipathd: dm-5: add map (uevent)
> Apr 24 20:27:40 cerebro multipathd: dm-5: devmap already registered
> #############
> 
> 
> My idea is set dm-multipath to only change from a path if it fails.
> How can I do that?
> 
> Any comments, doubts or suggest for this config would be appreciated
> as i'm new to all this hardware/setup.
> 
> Thanks in advance.
> 
> --
> 
> Flávio do Carmo Júnior aka waKKu
> 
> --
> dm-devel mailing list
> dm-devel redhat com
> https://www.redhat.com/mailman/listinfo/dm-devel


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