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DM-MIRROR added to arc-modules

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This is based on this good-old post from Totalnas: h*t*t*p*s*://xpenology.com/forum/topic/418-kernel-hijack/?do=findComment&comment=3715



The problem is that the Synology kernel doesn't include by default the kernel module to support the "pvmove" LVM command. And YES, this is required to shrink volumes and change disks without touching/removing/deleting the volumes (I'll explain it in the future).


So I've created a patch for the AuxXxilium/arc-modules to generate the modules (dm-mirror.ko, dm-log.ko and dm-region-hash.ko). The patch is at the end. More or less is very simple: for the kernel sources it adds the modules and compile it (I've only added the changes for the "broadwellnk-4.4.302" platform (DSM 7.2 with DS3622xs+)). Therefore, I suggest to add it to the main repository and promote it to all platforms. Then you can use it when using the good ARC Loader. You agree?


So please PocoPico and AuxXxilium can you merge this patch to https://github.com/AuxXxilium/arc-modules ?

Thank you.


dm-mirror-broadwellnk-4.4.302.zip dm-mirror.patch

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On 7/17/2023 at 5:43 PM, pocopico said:

Hi, thanks for the message,


I'm trying to identify the purpose for something like that. Why would you want to perform an XXmove command on Syno ? Can you please elaborate some more ? 



Thank you for sharing my patch with the github user. However, to fully use the patch it's necessary to promote it to the rest of platforms and generate the binaries and include them inside ARC loader as a custom modules. Futhermore, a simple insmod perhaps could be interesting to execute it at boot.


Regarding the use of this, I'll prepare a guide to shrink disks. In the meantime think on this: When you have a LVM group (vg1) to can attach ANY other device to it (after a simple "pvcreate /dev/XXX"). And then you can "move" (with "lvm pvmove /dev/SRE /dev/DST"). All in realtime. Therefore with these "missing" modules, you can continue using the volumes when moving them to a different device. The trick is then: 1) shrink the volumes; 2) shrink the LVM containers; 3) add new scratch space to the LVM group; 4) move the volumes to the new space (dm-mirror required); 5) remove the old disks from the LVM; 6) attach "new" (smaller) disks; 7) setup the new disks without creating a new group (or remove the one created); 8 ) manually add the new disks to the LVM group; 9) re-move the volumes to the new space (dm-mirror required again); 10) remove the scratch space from the LVM group... 11) reboot. The "new" LVM group will take the space the smaller disks.


I hope soon all RP loaders will include these necessary modules.



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