Few questions

Few questions

[Michael Makuch]

I realize this is the developers list and though I am a developer I'm 
not a developer
of linux raid, but I can find no other source of answers to these questions:

I've been using linux software raid (5) for a couple of years, having 
recently uped
to the 2.6.23 kernel (FC7, was previously on FC5). I just noticed that
my /proc/mdstat shows

$ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 etherd/e0.0[0] etherd/e0.2[9](S) etherd/e0.9[8] 
etherd/e0.8[7] etherd/e0.7[6] etherd/e0.6[5] etherd/e0.5[4] 
etherd/e0.4[3] etherd/e0.3[2] etherd/e0.1[1]
      3907091968 blocks level 5, 64k chunk, algorithm 2 [9/9] [UUUUUUUUU]
      [============>........]  resync = 64.5% (315458352/488386496) 
finish=2228.0min speed=1292K/sec
unused devices: <none>

and I have no idea where the raid6 came from. The only thing I've found 
on raid6
is a wikipedia.org page, nothing on 
http://tldp.org/HOWTO/Software-RAID-HOWTO.html

So my questions are:

- Is raid6 documented anywhere? If so, where? I'd like to take advantage 
of it if
it's really there.
- Why does my array (which I configured as raid5) have personalities of
raid6 (I can understand why raid4 would be there)?
- Is this a.o.k for a raid5 array?

Thanks

RE: Few questions

[Guy Watkins]

man md
man mdadm

I use RAID6.  Happy with it so far, but haven't had a disk failure yet.
RAID5 sucks because if you have 1 failed disk and 1 bad block on any other
disk, you are hosed.

Hope that helps.

} -----Original Message-----
} From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
} owner@vger.kernel.org] On Behalf Of Michael Makuch
} Sent: Friday, December 07, 2007 7:12 PM
} To: linux-raid@vger.kernel.org
} Subject: Few questions
} 
} I realize this is the developers list and though I am a developer I'm
} not a developer
} of linux raid, but I can find no other source of answers to these
} questions:
} 
} I've been using linux software raid (5) for a couple of years, having
} recently uped
} to the 2.6.23 kernel (FC7, was previously on FC5). I just noticed that
} my /proc/mdstat shows
} 
} $ cat /proc/mdstat
} Personalities : [raid6] [raid5] [raid4]
} md0 : active raid5 etherd/e0.0[0] etherd/e0.2[9](S) etherd/e0.9[8]
} etherd/e0.8[7] etherd/e0.7[6] etherd/e0.6[5] etherd/e0.5[4]
} etherd/e0.4[3] etherd/e0.3[2] etherd/e0.1[1]
}       3907091968 blocks level 5, 64k chunk, algorithm 2 [9/9] [UUUUUUUUU]
}       [============>........]  resync = 64.5% (315458352/488386496)
} finish=2228.0min speed=1292K/sec
} unused devices: <none>
} 
} and I have no idea where the raid6 came from. The only thing I've found
} on raid6
} is a wikipedia.org page, nothing on
} http://tldp.org/HOWTO/Software-RAID-HOWTO.html
} 
} So my questions are:
} 
} - Is raid6 documented anywhere? If so, where? I'd like to take advantage
} of it if
} it's really there.
} - Why does my array (which I configured as raid5) have personalities of
} raid6 (I can understand why raid4 would be there)?
} - Is this a.o.k for a raid5 array?
} 
} Thanks
} -
} To unsubscribe from this list: send the line "unsubscribe linux-raid" in
} the body of a message to majordomo@vger.kernel.org
} More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: Few questions

[Corey Hickey]

Michael Makuch wrote:
> I realize this is the developers list and though I am a developer I'm 
> not a developer
> of linux raid, but I can find no other source of answers to these questions:

Don't worry; it's a user list too.

> $ cat /proc/mdstat
> Personalities : [raid6] [raid5] [raid4]
> md0 : active raid5 etherd/e0.0[0] etherd/e0.2[9](S) etherd/e0.9[8] 
> etherd/e0.8[7] etherd/e0.7[6] etherd/e0.6[5] etherd/e0.5[4] 
> etherd/e0.4[3] etherd/e0.3[2] etherd/e0.1[1]
>       3907091968 blocks level 5, 64k chunk, algorithm 2 [9/9] [UUUUUUUUU]
>       [============>........]  resync = 64.5% (315458352/488386496) 
> finish=2228.0min speed=1292K/sec
> unused devices: <none>
> 
> and I have no idea where the raid6 came from.

As far as I understand, the "Personalities" line just shows what RAID
capabilities are compiled into the kernel (and loaded, if modules). For
example, even though I'm only using raid0, I have:

-----------------------------------------------------------------
$ cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md0 : active raid0 sdc[0] sdb[1]
      976772992 blocks 64k chunks

unused devices: <none>
-----------------------------------------------------------------

-Corey

Re: Few questions

[David Greaves]

Guy Watkins wrote:
> man md
> man mdadm
and
http://linux-raid.osdl.org/index.php/Main_Page

:)

/proc/mdstat docs (was Re: Few questions)

[David Greaves]

Michael Makuch wrote:
> So my questions are:
...
> - Is this a.o.k for a raid5 array?

So I realised that /proc/mdstat isn't documented too well anywhere...

http://linux-raid.osdl.org/index.php/Mdstat

Comments welcome...

David

Re: /proc/mdstat docs (was Re: Few questions)

[Raz]

many thanks . david.
It is very useful.

On 12/8/07, David Greaves <david@dgreaves.com> wrote:
> Michael Makuch wrote:
> > So my questions are:
> ...
> > - Is this a.o.k for a raid5 array?
>
> So I realised that /proc/mdstat isn't documented too well anywhere...
>
> http://linux-raid.osdl.org/index.php/Mdstat
>
> Comments welcome...
>
> David
> -
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>


-- 
Raz

Re: /proc/mdstat docs (was Re: Few questions)

[Michael Makuch]

David Greaves wrote:
> Michael Makuch wrote:
>   
>> So my questions are:
>>     
> ...
>   
>> - Is this a.o.k for a raid5 array?
>>     
>
> So I realised that /proc/mdstat isn't documented too well anywhere...
>
> http://linux-raid.osdl.org/index.php/Mdstat
>
> Comments welcome...
>
> David
>   

One thing, in the section "md device line" you describe how to identify 
spare devices,
but you didn't mention the "(S)" which appears after a spare device, at 
least it does on mine:

# uname -a
Linux pecan.makuch.org 2.6.23.1-21.fc7 #1 SMP Thu Nov 1 21:09:24 EDT 
2007 i686 i686 i386 GNU/Linux

# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 etherd/e0.0[0] etherd/e0.2[9](S) etherd/e0.9[8] 
etherd/e0.8[7] etherd/e0.7[6] etherd/e0.6[5] etherd/e0.5[4] 
etherd/e0.4[3] etherd/e0.3[2] etherd/e0.1[1]
      3907091968 blocks level 5, 64k chunk, algorithm 2 [9/9] [UUUUUUUUU]
      [==================>..]  resync = 91.0% (444527040/488386496) 
finish=560.9min speed=1301K/sec
unused devices: <none>


Unless that means something else??? But e0.2 is my spare so I'm just 
assuming "(S)" means spare!

Thanks
Mike

Re: Few questions

[Michael Makuch]

Guy Watkins wrote:
> man md
> man mdadm
>
> I use RAID6.  Happy with it so far, but haven't had a disk failure yet.
> RAID5 sucks because if you have 1 failed disk and 1 bad block on any other
> disk, you are hosed.
>
> Hope that helps.
I can't believe I've been using a raid array for 2 years and didn't know 
'man md' was there. I've
lived and breathed off of Software-RAID-HOWTO.html but it never mentions it.

Just a suggestion to whom it may concern: it might be nice to mention 
'man md' in the Howto as well
as the wiki pages.

Thanks

Mike