udev and mdadm -- I'm lost

udev and mdadm -- I'm lost

[AndyLiebman]

Sorry to pose this question but a  search through "man mdadm" the linux-raid 
archives and google didn't really get  me a very satisfactory answer. 

I guess I'm accustomed to working on  Linux systems with devfs. But now I had 
to upgrade to a distribution with udev.  I didn't notice any issues with 
mdadm until today, when I was working on a  server that was going to have two 
separate Software RAID-0 arrays (each striping  two 3ware Hardware RAID-5s). 

Lo and behold, I got the "/dev/md1 doesn't  exist" error when I tried to 
assemble /dev/md1. 

I see there is an mdadm  --auto option now, but I don't feel confident I know 
how to use it. Can someone  tell me the correct way to create or assemble an 
array with the --auto option?  

I don't want to do anything fancy. I don't need partitionable RAIDS. Do  I 
HAVE to specify a device number? 

It would just be nice to have a  couple of concrete examples of the proper 
syntax in "man mdadm"

If you  see this, Neil, I think you do a fantastic job. I'm sorry to ask this 
basic  question, but just one example in the manual would be welcome. I am 
using mdadm  1.9.0 and don't see one. 

i.e, 

mdadm -Av -a1 --uuid=xxxxx  /dev/sd*
or 
mdadm -Av -a /dev/md1 --uuid=xxxxx /dev/sd*

I'm not in  the mood to guess... 

Thanks. 

Andy Liebman  

Re: udev and mdadm -- I'm lost

[Sandro Dentella]

> 
> i.e, 
> 
> mdadm -Av -a1 --uuid=xxxxx  /dev/sd*
> or 
> mdadm -Av -a /dev/md1 --uuid=xxxxx /dev/sd*
> 
> I'm not in  the mood to guess... 

here is my personal example

	mdadm --create /dev/md0 -l1 -n2 --auto=yes /dev/sd*


*:-)

-- 
Sandro Dentella  *:-)
e-mail: sandro@e-den.it 
http://www.tksql.org                    TkSQL Home page - My GPL work

Re: udev and mdadm -- I'm lost

[Dave Jiang]

AndyLiebman@aol.com wrote:
> I see there is an mdadm  --auto option now, but I don't feel confident I know 
> how to use it. Can someone  tell me the correct way to create or assemble an 
> array with the --auto option?  
> 
> i.e, 
> 
> mdadm -Av -a1 --uuid=xxxxx  /dev/sd*
> or 
> mdadm -Av -a /dev/md1 --uuid=xxxxx /dev/sd*
> 
> I'm not in  the mood to guess... 
> 
> Thanks. 
> 
> Andy Liebman  

Just use --auto or --auto=yes and it should take care of the device node 
  creations. I have a /etc/mdadm.conf so I just do:
mdadm -As --auto=yes and it brings everything up over udev.

Although if you want to use the scan option with auto you may want to 
use mdadm 1.12.0 or later as on some of the earlier version the 
combination doesn't work.

-- 

------------------------------------------------------
Dave Jiang
Software Engineer, Carrier Grade Software
MontaVista Software, Inc.
http://www.mvista.com
------------------------------------------------------

Re: udev and mdadm -- I'm lost

[Konstantin Olchanski]

On Tue, Nov 08, 2005 at 04:40:23PM -0700, Dave Jiang wrote:
> >I see there is an mdadm  --auto option now...
> 
> Just use --auto or --auto=yes and it should take care of the device node 
>  creations. I have a /etc/mdadm.conf so I just do:
> mdadm -As --auto=yes and it brings everything up over udev.

I face a similar problem each time I use KNOPPIX to revive a non-booting
server. It always takes me 10-20 minutes to figure out the right
mdadm incantation to start the md devices. It does not help that mdadm
wants an /etc/mdadm.conf which is on an md device itself, unaccessible.

I wish there were a simple command to find and start all md devices, something
along the lines of:

mdadm --please-find-and-start-all-my-md-devices-please-please-please
or
mdadm --start-all, or whatever.

-- 
Konstantin Olchanski
Data Acquisition Systems: The Bytes Must Flow!
Email: olchansk-at-triumf-dot-ca
Snail mail: 4004 Wesbrook Mall, TRIUMF, Vancouver, B.C., V6T 2A3, Canada

Re: udev and mdadm -- I'm lost

[Bill Davidsen]

Konstantin Olchanski wrote:

>On Tue, Nov 08, 2005 at 04:40:23PM -0700, Dave Jiang wrote:
>  
>
>>>I see there is an mdadm  --auto option now...
>>>      
>>>
>>Just use --auto or --auto=yes and it should take care of the device node 
>> creations. I have a /etc/mdadm.conf so I just do:
>>mdadm -As --auto=yes and it brings everything up over udev.
>>    
>>
>
>I face a similar problem each time I use KNOPPIX to revive a non-booting
>server. It always takes me 10-20 minutes to figure out the right
>mdadm incantation to start the md devices. It does not help that mdadm
>wants an /etc/mdadm.conf which is on an md device itself, unaccessible.
>  
>
Hate to say it, that's a reward of a poor config choice and should be fixed.

>I wish there were a simple command to find and start all md devices, something
>along the lines of:
>
>mdadm --please-find-and-start-all-my-md-devices-please-please-please
>or
>mdadm --start-all, or whatever.
>
>  
>


-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979

Re: udev and mdadm -- I'm lost

[AndyLiebman]

>Just use --auto or --auto=yes and it should  take care of the device node 
> creations. I have a /etc/mdadm.conf  so I just do:
>mdadm -As --auto=yes and it brings everything up over  udev.
>
>Although if you want to use the scan option with auto you  may want to 
>use mdadm 1.12.0 or later as on some of the earlier version  the 
>combination doesn't work.  

Thank you Dave for your suggestion. Before you wrote back, I went ahead and  
tried out: 
 
mdadm -Av -amd 1 --uuid=xxxxx /dev/sd*
 
and that seemed to work. Is that okay. Unfortunately, "man mdadm" doesn't  
explain in much detail what the "yes" and "no" options do, unless I missed  
something. But the "md" option seems to make mdadm behave like it used to under  
devfs -- right? Only rather than specifing a device with the syntax "/dev/mdXX" 
 you just use "XX" or "X". 
 
It's not complicated, but it would be good to just know I'm doing it right. 
 
Andy