Re: [dm-devel] dm target options

[Kevin Corry <kevcorry us ibm com>]

Hi Andy,

On Thu March 3 2005 12:15 pm, Andy wrote:
> Is there any documentation that gives the format and options for the dm
> targets table?  I'm trying to setup a mirror target, but can't find a lot
> of information about it, and what the options mean.  Is dm-mirror good for
> production use, or should I just use md for mirroring?

There probably isn't any formal documents for the dm-mirror target. Looking at 
drivers/md/dm-raid1.c::mirror_ctr() in the kernel tree, the current table 
format is:

<start_lba> <size_in_sectors> mirror <log_type> <#_log_params> <log_params> \
   <#_mirrors> [<mirror_path> <starting_lba>]{2,}

where <log_type> is "core" or "disk".
<#_log_params> is 0 for the "core" log, and thus there is no <log_params> 
entry.
<#_log_params> is 2 or 3, and the <log_params> is:
  <log_device_path> <region_size> [<sync|nosync>]?

However, dm-mirror is primary used for pe-move in LVM2 and EVMS right now. 
There's still some improvements that will need to be made before it can be a 
full replacement for MD RAID-1. So if you're looking for something to use 
immediately, I'd stick with the MD driver for RAID functionality.

-- 
Kevin Corry
kevcorry us ibm com
http://www.ibm.com/linux/ltc/
http://evms.sourceforge.net/