[dm-devel] [code] prio_callout for r/w and r/o devices
Flavio Junior
billpp at gmail.com
Thu May 7 22:22:47 UTC 2009
Hi folks,
Based on the scenario i've described below I wrote a simple, totally based
on pp_rdac.c, code to send a SCSI command WRITE_AND_VERITY (0x2E) and decide
if that path is read-write or read-only.
The code is here: http://pastebin.com/m22b06f04
I'm sending it to the list to request for improve, tips, recommendations,
anything... I'm not a developer anyway.
--
Flávio do Carmo Júnior aka waKKu
On Fri, Apr 24, 2009 at 11:21 PM, Flavio Junior <billpp at gmail.com> wrote:
> On Fri, Apr 24, 2009 at 10:24 PM, Chandra Seetharaman
> <sekharan at us.ibm.com> wrote:
> > Hi Flavio,
>
> Hi Chandra ;)
>
> >
> > 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 ?
>
> I'm using dm-multipath to group LUN's at different storages. But, IBM
> DS4700 ERM just allows (really makes sense) read-write operations on
> the primary storage device, so this is why I need to different prio
> for paths.
>
> >
> > >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.
>
> Yes, exactly is. But the LSI RDAC driver is doing the one multipath
> channel (channel-A) for the the read-write LUN's (all r/w LUN's are in
> the same primary storage and have the same scsi_id) and another
> multipath channel (channel-B) for all read-only LUN's (all r/o LUN's
> are in the same *secundary* storage and have the same scsi_id).
>
> So, I've 2 devices that says to be the "same" by ERM, but one as
> primary=rw and another as secundary=ro, to reach primary i've
> channel-A and reach secundary i've channel-B.
>
> What I'm doing is: Grouping channel-A + channel-B into a single mpath
> device, and it is working as expected (i dont know if someone that
> really know about it would consider me a freak-crazy man, but it
> works).
>
> >
> > 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.
> >
>
> Here you figure out my problem with annoying log messages :). So I'd
> understand i need to change prio when changing storage
> primary/secundary role. :)
>
>
> > 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 :)
> >
> Ouch! ... I almost go into a infinity loop here ;).
>
>
> Well, you point my problem, now i'll think someway to calculate prio
> (inside that really restrict namespace) dynamically when changing the
> path.
>
> Really thanks, you make things a bit clear for me :).
>
> And if you (or anyone else) understand my scenario and knows it is not
> a good approach, please let me know before start production.
>
> Thanks all.
>
> --
>
> Flávio do Carmo Júnior aka waKKu
>
> >
> > 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 at 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 at 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 at 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 at redhat.com
> >> https://www.redhat.com/mailman/listinfo/dm-devel
> >
> > --
> > dm-devel mailing list
> > dm-devel at redhat.com
> > https://www.redhat.com/mailman/listinfo/dm-devel
> >
>
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