* write directly to device mapper snapshot origin device ? @ 2016-07-14 14:25 Navin P.S 2016-07-15 8:29 ` Navin P.S 0 siblings, 1 reply; 9+ messages in thread From: Navin P.S @ 2016-07-14 14:25 UTC (permalink / raw) To: dm-devel Hi, Can i do dd if=/dev/zero of=/dev/mapper/dmo count=20 ? where dmo is a dm snapshot origin created through dmsetup command. Instead of /dev/zero i can write valid devices. I could create the dmo through some lvm2 commands. Is direct write with 4k (page size values ) allowed when it is mapped to 2 block devices in linear mode ? Regards, -- Navin ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: write directly to device mapper snapshot origin device ? 2016-07-14 14:25 write directly to device mapper snapshot origin device ? Navin P.S @ 2016-07-15 8:29 ` Navin P.S 2016-07-15 11:51 ` Mikulas Patocka 0 siblings, 1 reply; 9+ messages in thread From: Navin P.S @ 2016-07-15 8:29 UTC (permalink / raw) To: dm-devel, snitzer, mpatocka Resend .. On Thu, Jul 14, 2016 at 7:55 PM, Navin P.S <navinp1912@gmail.com> wrote: > Hi, > Can i do dd if=/dev/zero of=/dev/mapper/dmo count=20 ? where dmo is > a dm snapshot origin created through dmsetup command. Instead of > /dev/zero i can write valid devices. > > I could create the dmo through some lvm2 commands. Is direct write > with 4k (page size values ) allowed when it is mapped to 2 block > devices in linear mode ? > > > Regards, > -- Navin I'm seeing OOM followed by reboot of host machine. Does this mean this device cannot to exported to containers for writing ? -- -- Navin ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: write directly to device mapper snapshot origin device ? 2016-07-15 8:29 ` Navin P.S @ 2016-07-15 11:51 ` Mikulas Patocka 2016-07-15 12:15 ` Navin P.S 0 siblings, 1 reply; 9+ messages in thread From: Mikulas Patocka @ 2016-07-15 11:51 UTC (permalink / raw) To: Navin P.S; +Cc: dm-devel, snitzer On Fri, 15 Jul 2016, Navin P.S wrote: > Resend .. > > On Thu, Jul 14, 2016 at 7:55 PM, Navin P.S <navinp1912@gmail.com> wrote: > > Hi, > > Can i do dd if=/dev/zero of=/dev/mapper/dmo count=20 ? where dmo is > > a dm snapshot origin created through dmsetup command. Instead of > > /dev/zero i can write valid devices. > > > > I could create the dmo through some lvm2 commands. lvcreate -s > > Is direct write > > with 4k (page size values ) allowed when it is mapped to 2 block > > devices in linear mode ? > > > > > > Regards, > > -- Navin > > I'm seeing OOM followed by reboot of host machine. > Does this mean this device cannot to exported to containers for writing ? The snapshot driver requires 32 bytes of memory for one chunk (the chunk size is selected with the "-c" switch to lvcreate). You should set system memory according to that. Mikulas > -- Navin > ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: write directly to device mapper snapshot origin device ? 2016-07-15 11:51 ` Mikulas Patocka @ 2016-07-15 12:15 ` Navin P.S 2016-07-15 12:35 ` Zdenek Kabelac 2016-07-15 13:50 ` Mikulas Patocka 0 siblings, 2 replies; 9+ messages in thread From: Navin P.S @ 2016-07-15 12:15 UTC (permalink / raw) To: Mikulas Patocka; +Cc: dm-devel, snitzer On Fri, Jul 15, 2016 at 5:21 PM, Mikulas Patocka <mpatocka@redhat.com> wrote: > > > On Fri, 15 Jul 2016, Navin P.S wrote: > >> Resend .. >> >> On Thu, Jul 14, 2016 at 7:55 PM, Navin P.S <navinp1912@gmail.com> wrote: >> > Hi, >> > Can i do dd if=/dev/zero of=/dev/mapper/dmo count=20 ? where dmo is >> > a dm snapshot origin created through dmsetup command. Instead of >> > /dev/zero i can write valid devices. >> > >> > I could create the dmo through some lvm2 commands. > > lvcreate -s > >> > Is direct write >> > with 4k (page size values ) allowed when it is mapped to 2 block >> > devices in linear mode ? >> > >> > >> > Regards, >> > -- Navin >> >> I'm seeing OOM followed by reboot of host machine. >> Does this mean this device cannot to exported to containers for writing ? > > The snapshot driver requires 32 bytes of memory for one chunk (the chunk > size is selected with the "-c" switch to lvcreate). You should set system > memory according to that. > > Mikulas > >> -- Navin >> Are origin devices readonly ? When i do dd if=/dev/zero of=/dev/mapper/ff count=10, it kills all the process says OOM. How do you go about debugging this ? I'm running 4.7.0-rc7+ . root@vm-xenial-foo:~# dmsetup info Name: cryptie4-ff State: ACTIVE Read Ahead: 256 Tables present: LIVE Open count: 0 Event number: 0 Major, minor: 251, 0 Number of targets: 2 Name: ff State: ACTIVE Read Ahead: 256 Tables present: LIVE Open count: 0 Event number: 0 Major, minor: 251, 1 Number of targets: 1 root@vm-xenial-foo:~# dmsetup status cryptie4-ff: 0 102400 linear cryptie4-ff: 102400 122880 linear ff: 0 102400 snapshot-origin root@vm-xenial-foo:~# free -m total used free shared buff/cache available Mem: 7762 2178 3720 358 1864 4920 Swap: 19145 0 19145 -- -- Navin ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: write directly to device mapper snapshot origin device ? 2016-07-15 12:15 ` Navin P.S @ 2016-07-15 12:35 ` Zdenek Kabelac 2016-07-15 12:40 ` Navin P.S 2016-07-15 13:50 ` Mikulas Patocka 1 sibling, 1 reply; 9+ messages in thread From: Zdenek Kabelac @ 2016-07-15 12:35 UTC (permalink / raw) To: Navin P.S; +Cc: dm-devel Dne 15.7.2016 v 14:15 Navin P.S napsal(a): > On Fri, Jul 15, 2016 at 5:21 PM, Mikulas Patocka <mpatocka@redhat.com> wrote: >> >> >> On Fri, 15 Jul 2016, Navin P.S wrote: >> >>> Resend .. >>> >>> On Thu, Jul 14, 2016 at 7:55 PM, Navin P.S <navinp1912@gmail.com> wrote: >>>> Hi, >>>> Can i do dd if=/dev/zero of=/dev/mapper/dmo count=20 ? where dmo is >>>> a dm snapshot origin created through dmsetup command. Instead of >>>> /dev/zero i can write valid devices. >>>> >>>> I could create the dmo through some lvm2 commands. >> >> lvcreate -s >> >>>> Is direct write >>>> with 4k (page size values ) allowed when it is mapped to 2 block >>>> devices in linear mode ? >>>> >>>> >>>> Regards, >>>> -- Navin >>> >>> I'm seeing OOM followed by reboot of host machine. >>> Does this mean this device cannot to exported to containers for writing ? >> >> The snapshot driver requires 32 bytes of memory for one chunk (the chunk >> size is selected with the "-c" switch to lvcreate). You should set system >> memory according to that. >> >> Mikulas >> >>> -- Navin >>> > > > > > Are origin devices readonly ? > > When i do dd if=/dev/zero of=/dev/mapper/ff count=10, it kills all the > process says OOM. > > How do you go about debugging this ? I'm running 4.7.0-rc7+ . > > > root@vm-xenial-foo:~# dmsetup info > Name: cryptie4-ff > State: ACTIVE > Read Ahead: 256 > Tables present: LIVE > Open count: 0 > Event number: 0 > Major, minor: 251, 0 > Number of targets: 2 > > Name: ff > State: ACTIVE > Read Ahead: 256 > Tables present: LIVE > Open count: 0 > Event number: 0 > Major, minor: 251, 1 > Number of targets: 1 > > root@vm-xenial-foo:~# dmsetup status > cryptie4-ff: 0 102400 linear > cryptie4-ff: 102400 122880 linear > ff: 0 102400 snapshot-origin > root@vm-xenial-foo:~# Hi Maybe you should have started with reading documenation for snapshot target ? linux/Documentation/device-mapper/snapshot.txt If you don't like to read much doc - I'd highly recommend to stay at 'lvm2' command level and create snapshot via 'lvcreate -s' Regards Zdenek ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: write directly to device mapper snapshot origin device ? 2016-07-15 12:35 ` Zdenek Kabelac @ 2016-07-15 12:40 ` Navin P.S 2016-07-15 12:44 ` Zdenek Kabelac 0 siblings, 1 reply; 9+ messages in thread From: Navin P.S @ 2016-07-15 12:40 UTC (permalink / raw) To: Zdenek Kabelac; +Cc: dm-devel On Fri, Jul 15, 2016 at 6:05 PM, Zdenek Kabelac <zkabelac@redhat.com> wrote: > Dne 15.7.2016 v 14:15 Navin P.S napsal(a): > >> On Fri, Jul 15, 2016 at 5:21 PM, Mikulas Patocka <mpatocka@redhat.com> >> wrote: >>> >>> >>> >>> On Fri, 15 Jul 2016, Navin P.S wrote: >>> >>>> Resend .. >>>> >>>> On Thu, Jul 14, 2016 at 7:55 PM, Navin P.S <navinp1912@gmail.com> wrote: >>>>> >>>>> Hi, >>>>> Can i do dd if=/dev/zero of=/dev/mapper/dmo count=20 ? where dmo is >>>>> a dm snapshot origin created through dmsetup command. Instead of >>>>> /dev/zero i can write valid devices. >>>>> >>>>> I could create the dmo through some lvm2 commands. >>> >>> >>> lvcreate -s >>> >>>>> Is direct write >>>>> with 4k (page size values ) allowed when it is mapped to 2 block >>>>> devices in linear mode ? >>>>> >>>>> >>>>> Regards, >>>>> -- Navin >>>> >>>> >>>> I'm seeing OOM followed by reboot of host machine. >>>> Does this mean this device cannot to exported to containers for writing >>>> ? >>> >>> >>> The snapshot driver requires 32 bytes of memory for one chunk (the chunk >>> size is selected with the "-c" switch to lvcreate). You should set system >>> memory according to that. >>> >>> Mikulas >>> >>>> -- Navin >>>> >> >> >> >> >> Are origin devices readonly ? >> >> When i do dd if=/dev/zero of=/dev/mapper/ff count=10, it kills all the >> process says OOM. >> >> How do you go about debugging this ? I'm running 4.7.0-rc7+ . >> >> >> root@vm-xenial-foo:~# dmsetup info >> Name: cryptie4-ff >> State: ACTIVE >> Read Ahead: 256 >> Tables present: LIVE >> Open count: 0 >> Event number: 0 >> Major, minor: 251, 0 >> Number of targets: 2 >> >> Name: ff >> State: ACTIVE >> Read Ahead: 256 >> Tables present: LIVE >> Open count: 0 >> Event number: 0 >> Major, minor: 251, 1 >> Number of targets: 1 >> >> root@vm-xenial-foo:~# dmsetup status >> cryptie4-ff: 0 102400 linear >> cryptie4-ff: 102400 122880 linear >> ff: 0 102400 snapshot-origin >> root@vm-xenial-foo:~# > > > Hi > > Maybe you should have started with reading documenation for snapshot target > ? > > linux/Documentation/device-mapper/snapshot.txt > It nowhere mentions that origin device is readonly. It says writes go to COW device and then you can merge it back. Can you please paste the snippet ? ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: write directly to device mapper snapshot origin device ? 2016-07-15 12:40 ` Navin P.S @ 2016-07-15 12:44 ` Zdenek Kabelac 2016-07-15 18:58 ` Navin P.S 0 siblings, 1 reply; 9+ messages in thread From: Zdenek Kabelac @ 2016-07-15 12:44 UTC (permalink / raw) To: Navin P.S; +Cc: dm-devel Dne 15.7.2016 v 14:40 Navin P.S napsal(a): > On Fri, Jul 15, 2016 at 6:05 PM, Zdenek Kabelac <zkabelac@redhat.com> wrote: >> Dne 15.7.2016 v 14:15 Navin P.S napsal(a): >> >>> On Fri, Jul 15, 2016 at 5:21 PM, Mikulas Patocka <mpatocka@redhat.com> >>> wrote: >>>> >>>> >>>> >>>> On Fri, 15 Jul 2016, Navin P.S wrote: >>>> >>>>> Resend .. >>>>> >>>>> On Thu, Jul 14, 2016 at 7:55 PM, Navin P.S <navinp1912@gmail.com> wrote: >>>>>> >>>>>> Hi, >>>>>> Can i do dd if=/dev/zero of=/dev/mapper/dmo count=20 ? where dmo is >>>>>> a dm snapshot origin created through dmsetup command. Instead of >>>>>> /dev/zero i can write valid devices. >>>>>> >>>>>> I could create the dmo through some lvm2 commands. >>>> >>>> >>>> lvcreate -s >>>> >>>>>> Is direct write >>>>>> with 4k (page size values ) allowed when it is mapped to 2 block >>>>>> devices in linear mode ? >>>>>> >>>>>> >>>>>> Regards, >>>>>> -- Navin >>>>> >>>>> >>>>> I'm seeing OOM followed by reboot of host machine. >>>>> Does this mean this device cannot to exported to containers for writing >>>>> ? >>>> >>>> >>>> The snapshot driver requires 32 bytes of memory for one chunk (the chunk >>>> size is selected with the "-c" switch to lvcreate). You should set system >>>> memory according to that. >>>> >>>> Mikulas >>>> >>>>> -- Navin >>>>> >>> >>> >>> >>> >>> Are origin devices readonly ? >>> >>> When i do dd if=/dev/zero of=/dev/mapper/ff count=10, it kills all the >>> process says OOM. >>> >>> How do you go about debugging this ? I'm running 4.7.0-rc7+ . >>> >>> >>> root@vm-xenial-foo:~# dmsetup info >>> Name: cryptie4-ff >>> State: ACTIVE >>> Read Ahead: 256 >>> Tables present: LIVE >>> Open count: 0 >>> Event number: 0 >>> Major, minor: 251, 0 >>> Number of targets: 2 >>> >>> Name: ff >>> State: ACTIVE >>> Read Ahead: 256 >>> Tables present: LIVE >>> Open count: 0 >>> Event number: 0 >>> Major, minor: 251, 1 >>> Number of targets: 1 >>> >>> root@vm-xenial-foo:~# dmsetup status >>> cryptie4-ff: 0 102400 linear >>> cryptie4-ff: 102400 122880 linear >>> ff: 0 102400 snapshot-origin >>> root@vm-xenial-foo:~# >> >> >> Hi >> >> Maybe you should have started with reading documenation for snapshot target >> ? >> >> linux/Documentation/device-mapper/snapshot.txt >> > > It nowhere mentions that origin device is readonly. It says writes go > to COW device > and then you can merge it back. > > Can you please paste the snippet ? 1) a device containing the original mapping table of the source volume; 2) a device used as the <COW device>; 3) a "snapshot" device, combining #1 and #2, which is the visible snapshot volume; 4) the "original" volume (which uses the device number used by the original source volume), whose table is replaced by a "snapshot-origin" mapping from device #1. Regards Zdenek ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: write directly to device mapper snapshot origin device ? 2016-07-15 12:44 ` Zdenek Kabelac @ 2016-07-15 18:58 ` Navin P.S 0 siblings, 0 replies; 9+ messages in thread From: Navin P.S @ 2016-07-15 18:58 UTC (permalink / raw) To: Zdenek Kabelac; +Cc: dm-devel On Fri, Jul 15, 2016 at 6:14 PM, Zdenek Kabelac <zkabelac@redhat.com> wrote: > Dne 15.7.2016 v 14:40 Navin P.S napsal(a): > >> On Fri, Jul 15, 2016 at 6:05 PM, Zdenek Kabelac <zkabelac@redhat.com> >> wrote: >>> >>> Dne 15.7.2016 v 14:15 Navin P.S napsal(a): >>> >>>> On Fri, Jul 15, 2016 at 5:21 PM, Mikulas Patocka <mpatocka@redhat.com> >>>> wrote: >>>>> >>>>> >>>>> >>>>> >>>>> On Fri, 15 Jul 2016, Navin P.S wrote: >>>>> >>>>>> Resend .. >>>>>> >>>>>> On Thu, Jul 14, 2016 at 7:55 PM, Navin P.S <navinp1912@gmail.com> >>>>>> wrote: >>>>>>> >>>>>>> >>>>>>> Hi, >>>>>>> Can i do dd if=/dev/zero of=/dev/mapper/dmo count=20 ? where dmo is >>>>>>> a dm snapshot origin created through dmsetup command. Instead of >>>>>>> /dev/zero i can write valid devices. >>>>>>> >>>>>>> I could create the dmo through some lvm2 commands. >>>>> >>>>> >>>>> >>>>> lvcreate -s >>>>> >>>>>>> Is direct write >>>>>>> with 4k (page size values ) allowed when it is mapped to 2 block >>>>>>> devices in linear mode ? >>>>>>> >>>>>>> >>>>>>> Regards, >>>>>>> -- Navin >>>>>> >>>>>> >>>>>> >>>>>> I'm seeing OOM followed by reboot of host machine. >>>>>> Does this mean this device cannot to exported to containers for >>>>>> writing >>>>>> ? >>>>> >>>>> >>>>> >>>>> The snapshot driver requires 32 bytes of memory for one chunk (the >>>>> chunk >>>>> size is selected with the "-c" switch to lvcreate). You should set >>>>> system >>>>> memory according to that. >>>>> >>>>> Mikulas >>>>> >>>>>> -- Navin >>>>>> >>>> >>>> >>>> >>>> >>>> Are origin devices readonly ? >>>> >>>> When i do dd if=/dev/zero of=/dev/mapper/ff count=10, it kills all the >>>> process says OOM. >>>> > >> >> Can you please paste the snippet ? > > > > 1) a device containing the original mapping table of the source volume; > 2) a device used as the <COW device>; > 3) a "snapshot" device, combining #1 and #2, which is the visible snapshot > volume; > 4) the "original" volume (which uses the device number used by the original > source volume), whose table is replaced by a "snapshot-origin" mapping > from device #1. > 1,2,3,4 doesn't say you can't write to snapshot-origin ? Does it ? If you setup the table with dmsetup -r explicitly it means readonly. Also if direct writes are not supposed to be done, only merging why not setup readonly and then create it in read-write during merging. -- -- Navin ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: write directly to device mapper snapshot origin device ? 2016-07-15 12:15 ` Navin P.S 2016-07-15 12:35 ` Zdenek Kabelac @ 2016-07-15 13:50 ` Mikulas Patocka 1 sibling, 0 replies; 9+ messages in thread From: Mikulas Patocka @ 2016-07-15 13:50 UTC (permalink / raw) To: Navin P.S; +Cc: dm-devel, snitzer > Are origin devices readonly ? > > When i do dd if=/dev/zero of=/dev/mapper/ff count=10, it kills all the > process says OOM. > > How do you go about debugging this ? I'm running 4.7.0-rc7+ . Find some older kernel where this worked. Use the git bisect tool on the kernel tree to find out which patch broke it. Mikulas > root@vm-xenial-foo:~# dmsetup info > Name: cryptie4-ff > State: ACTIVE > Read Ahead: 256 > Tables present: LIVE > Open count: 0 > Event number: 0 > Major, minor: 251, 0 > Number of targets: 2 > > Name: ff > State: ACTIVE > Read Ahead: 256 > Tables present: LIVE > Open count: 0 > Event number: 0 > Major, minor: 251, 1 > Number of targets: 1 > > root@vm-xenial-foo:~# dmsetup status > cryptie4-ff: 0 102400 linear > cryptie4-ff: 102400 122880 linear > ff: 0 102400 snapshot-origin > root@vm-xenial-foo:~# > > > > > free -m > total used free shared buff/cache available > Mem: 7762 2178 3720 358 1864 4920 > Swap: 19145 0 19145 > > > -- > -- Navin > ^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2016-07-15 18:58 UTC | newest] Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2016-07-14 14:25 write directly to device mapper snapshot origin device ? Navin P.S 2016-07-15 8:29 ` Navin P.S 2016-07-15 11:51 ` Mikulas Patocka 2016-07-15 12:15 ` Navin P.S 2016-07-15 12:35 ` Zdenek Kabelac 2016-07-15 12:40 ` Navin P.S 2016-07-15 12:44 ` Zdenek Kabelac 2016-07-15 18:58 ` Navin P.S 2016-07-15 13:50 ` Mikulas Patocka
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