snmpd strangeness

[Jeremy Chadwick]

On Wed, Nov 19, 2008 at 12:34:55PM -0500, John Almberg wrote:
>>> Now I'm curious about snmp, so perhaps I'll try to figure out how to 
>>> get
>>> it to something useful. This machine has 8 hard drives, and is  
>>> located in
>>> Manhattan, so I would certainly like to be informed if one of the  
>>> raid
>>> drives went on the blink. That was one of the things he was trying  
>>> to get
>>> working.
>>
>> Net-SNMP won't give you the status of the RAID.  Neither will bsnmpd 
>> (10.
>> FreeBSD simply does not have the hooks to make this possible.  Someone
>> needs to write the code.  I do not recommend relying on shell scripts
>> tied into Net-SNMP to accomplish this either (for a lot of very good
>> reasons); write the code in native C.
>>
>> It also greatly depends on what you're using for RAID.  If a hardware
>> controller, good luck getting the status out of an API natively (sans
>> Areca, which I believe offers an API) -- you'll resort to shell  
>> scripts
>> and CLI binaries, in which case you're *easily* better off with a
>> cronjob, periodic(8), or a log monitor daemon.
>
> This machine has an Intel motherboard and a hardware raid controller.  
> From what I can tell, there is some Intel software installed on the  
> machine that makes hardware faults visible to snmp.

That would require Net-SNMP to be linked to that software (or library)
directly.  Two things can't just "magically talk" to one another.  :-)

AFAIK, Intel does not provide such software on FreeBSD, but I could be
complete wrong here.  They primarily focus on Linux, like most companies
do.

> That last sentence makes it sound like I know more than I do about this 
> situation. I'm just reading from notes. :-)
>
> And I have an Intel disk that came with the motherboard that hints at  
> the same type of thing. I've just scanned the docs on the disk... looks 
> extraordinarily complicated.

I don't know what controller it is, but Net-SNMP doesn't have any sort
of out-of-the-box support for any kind of RAID card.  See above for
what's needed.

I just hope the card is an actual RAID card and not BIOS-level RAID like
Intel MatrixRAID.  If it is MatrixRAID, I highly recommend you back the
entire machine up and reinstall without MatrixRAID, otherwise when you
lose a disk or need to rebuild your array, you'll find your array
broken/gone, be completely unable to rebuild it, or kernel panics.  Note
that all of this stuff works just fine on Linux; the issues listed are
with FreeBSD.

Generally speaking, we (the open-source world) have gotten to the point
with OS-based software RAID (e.g. Linux LVM, FreeBSD ccd/gvinum/ZFS,
OpenSolaris ZFS) where it offers significant advantages over hardware
RAID.  There are good reasons to use hardware RAID, but in those
scenarios admins should be looking at buying an actual filer, e.g.
Network Appliance.  Otherwise, for "simple" systems (even stuff like
2U or 3U boxes with many disks, e.g. a "low-cost filer"), stick with
some form of OS-based software RAID if possible.

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |