RE: can't attach caching device to backing device

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Yes, the file does exist.

Should I try it with the individual devices in the array?

I don't suppose bcache can play with LVM?

- Justin

-----Original Message----- 
From: Kent Overstreet [kent.overstreet@xxxxxxxxx]
Received: Sunday, 20 Nov 2011, 11:31pm
To: Justin Rush [jarush@xxxxxxxx]
CC: linux-bcache@xxxxxxxxxxxxxxx [linux-bcache@xxxxxxxxxxxxxxx]
Subject: Re: can't attach caching device to backing device
When you tried to attach the cache, did the file you were echoing to
exist? That looks correct but I'm not sure what else would generate
that error.

For the UUIDs to show up in blkid, blkid itself would have to be
updated to know about the bcache superblock (IIRC it lives in
util-linux). I should probably ping the author and see if that can get
included.

If you have the udev rules and probe-bcache installed, the symlinks
/ought/ to show up when you reboot but I haven't tested that in ages.

I just got the code written so that it ought to be able to work on top
of md devices again, which means I should be able to run it at home
and I'll have to fix probe-bcache if it's broken then :)

On Mon, Nov 14, 2011 at 3:10 PM, Justin Rush <jarush@xxxxxxxx> wrote:
> Using 3.1.0-rc9
>
> I created a cache device on /dev/sdk1
> # ./make-bcache -C -b512k -w4k --writeback /dev/sdk1
>
> and a backing device on /dev/md127p1.
> ./make-bcache -B /dev/md127p1
>
> # ./probe-bcache /dev/sdk1
> 5f42bdd1-4342-4ab6-8dda-855989a09604: UUID="" TYPE="bcache"
>
> # ./probe-bcache /dev/md127p1
> 6bbac9a4-afbd-4d40-9562-cdd290622c5d: UUID="" TYPE="bcache"
>
> I then registered them by:
> # echo /dev/sdk1 >/sys/fs/bcache/register # echo /dev/md127p1 >/sys/fs/bcache/register
>
> I have /dev/bcache0
>
> When I try to attach the cache, I get this:
> # echo "5f42bdd1-4342-4ab6-8dda-855989a09604" >/sys/block/md127/md127p1/bcache/attach
> -bash: echo: write error: No such file or directory
>
> I believe this problem is due to the UUIDs for the two devices, but this is just a guess.  The UUID for /dev/sdk1 and /dev/md127p1 doesn't appear to be registering properly as they don't show up in blkid.  I tried specifying the UUID to use with the -U option when creating the devices, but that didn't seem to help.  I do have the udev rules file from the tools in place
>
> Does anyone know what is going on here and how to fix it?
>
> Justin Rush
> jarush@xxxxxxxx
>
>
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