Re: [linux-lvm] [data] Re: Setting up LVM cache causes crash

[Brassow Jonathan <jbrassow@redhat.com>]

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On Sep 3, 2014, at 11:29 AM, Elvin Cako wrote:

> I also want to add some discrepancies in looking at the file:
> 
> cat /proc/mdstat
> Personalities : [raid1] 
> ... 
> md35 : active raid1 sdb2[0] sdc2[1]
>       99629440 blocks super 1.0 [3/2] [UU_]
>       
> md34 : active raid1 sdbt2[0] sdbp2[1]
>       830240064 blocks super 1.0 [3/2] [UU_]
>       
> md33 : active raid1 sdbu2[0] sdbs2[1]
>       830240064 blocks super 1.0 [3/2] [UU_]
>       
> md32 : active raid1 sdby2[0] sdbv2[1]
>       830240064 blocks super 1.0 [3/2] [UU_]
>       
> md31 : active raid1 sdbr2[0] sdbw2[1]
>       830240064 blocks super 1.0 [3/2] [UU_]
>       
> md30 : active raid1 sdbq2[0] sdbx2[1]
>       830240064 blocks super 1.0 [3/2] [UU_]
> ... 
> 
> We are only using the second partition of each drive for our md devices. In the log(attached previously) we see that the drive, the first partition, and the second partition are "Added to device cache".  Is "device cache" some other cache not related to our SSD cache we're trying to create?
> 
> #device/dev-cache.c:333         /dev/sdb: Added to device cache
> #device/dev-cache.c:330         /dev/disk/by-id/ata-Samsung_SSD_840_EVO_120GB_S1D5NSBF109608M: Aliased to /dev/sdb in device cache
> #device/dev-cache.c:330         /dev/disk/by-id/wwn-0x50025388a01d30bc: Aliased to /dev/sdb in device cache
> #device/dev-cache.c:333         /dev/sdb1: Added to device cache
> #device/dev-cache.c:330         /dev/disk/by-id/ata-Samsung_SSD_840_EVO_120GB_S1D5NSBF109608M-part1: Aliased to /dev/sdb1 in device cache
> #device/dev-cache.c:330         /dev/disk/by-id/wwn-0x50025388a01d30bc-part1: Aliased to /dev/sdb1 in device cache
> #device/dev-cache.c:319         /dev/disk/by-partlabel/metadata: Already in device cache
> #device/dev-cache.c:330         /dev/disk/by-partuuid/e7d5c622-626c-4122-9d5c-ccb1ae1ff0dc: Aliased to /dev/sdb1 in device cache
> #device/dev-cache.c:330         /dev/disk/by-uuid/dc8f83e2-1073-4128-b64f-9e86b9539c67: Aliased to /dev/sdb1 in device cache
> #device/dev-cache.c:333         /dev/sdb2: Added to device cache
> #device/dev-cache.c:330         /dev/disk/by-id/ata-Samsung_SSD_840_EVO_120GB_S1D5NSBF109608M-part2: Aliased to /dev/sdb2 in device cache
> #device/dev-cache.c:330         /dev/disk/by-id/wwn-0x50025388a01d30bc-part2: Aliased to /dev/sdb2 in device cache
> #device/dev-cache.c:319         /dev/disk/by-partlabel/raiddata: Already in device cache
> #device/dev-cache.c:330         /dev/disk/by-partuuid/39bcecad-693c-4842-b71d-920c4eb8aaef: Aliased to /dev/sdb2 in device cache
>  

Yes, it is different.  That has to do with LVM remembering what devices it has seen when reading LVM labels.  The LVM labels on those devices tell it how the volumes have been constructed and so on.

 brassow


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