Re: qemu blocksize vs zvol? (was Re: qemu tricks and tips for working with VM?)

[mlelstv%serpens.de@localhost (Michael van Elst)]

riz%tastylime.net@localhost (Jeff Rizzo) writes:

>OK, I can seemingly confirm it's a sector/block size issue; when I copy 
>the zvol to a plain ("raw") file, it boots normally.

That would suggest that your zvol has an incompatible sector size.


>I tried zvols with volblocksize=512 and 4k (the original is 16k), but 

volblocksize isn't the right metric, that's more a "cluster size"
that determines space allocation.

# zfs get volblocksize tank/myvol
NAME        PROPERTY      VALUE     SOURCE
tank/myvol  volblocksize  8K        -

# dkctl /dev/zvol/rdsk/tank/myvol getgeometry
/dev/zvol/rdsk/tank/myvol: 214748364800 bytes in 52428800 blocks of 4096 bytes

N.B. I just added the getgeometry command to dkctl. Another method
is to abuse the gpt tool in verbose mode:

# gpt -v show  /dev/zvol/rdsk/tank/myvol
/dev/zvol/rdsk/tank/myvol: mediasize=214748364800; sectorsize=4096; blocks=52428800
/dev/zvol/rdsk/tank/myvol: MBR not found at sector 0
GPT not found, displaying data from MBR.

     start      size  index  contents
         0  52428800         Unused