On Fri, Jul 15, 2016 at 6:14 PM, Zdenek Kabelac <zkabelac@xxxxxxxxxx> 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@xxxxxxxxxx> >> 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@xxxxxxxxxx> >>>> wrote: >>>>> >>>>> >>>>> >>>>> >>>>> On Fri, 15 Jul 2016, Navin P.S wrote: >>>>> >>>>>> Resend .. >>>>>> >>>>>> On Thu, Jul 14, 2016 at 7:55 PM, Navin P.S <navinp1912@xxxxxxxxx> >>>>>> 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 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
