[Beowulf] Big storage

Bruce Allen ballen at gravity.phys.uwm.edu
Wed Apr 16 23:39:01 PDT 2008

Hi Gerry,

> Areca replacement; RAID rebuild (usually successful); backup; Areca 
> replacement with 3Ware controller or CoRAID (or JetStor) shelf; create 
> new RAID instance; restore from backup.
> Let's just say we lost confidence.

I understand.  Was this with 'current generation' controllers and firmware 
or was this two or three years ago?  It's my impression that (when used 
with compatible drives and drive backplanes) the latest generation of 
Areca hardware is quite stable.


> Bruce Allen wrote:
>> What was needed to fix the systems?  Reboot?  Hardware replacement?
>> On Wed, 16 Apr 2008, Gerry Creager wrote:
>>> We've had two fail rather randomly.  The failures did cause disk 
>>> corruption but it wasn't an undetected/undetectable sort.  They started 
>>> throwing errors to syslog, then fell over and stopped accessing disks.
>>> gerry
>>> Bruce Allen wrote:
>>>> Hi Gerry,
>>>> So far the only problem we have had is with one Areca card that had a bad 
>>>> 2GB memory module.  This generated lots of (correctable) single bit 
>>>> errors but eventually caused real problems.  Could you say something 
>>>> about the reliability issues you have seen?
>>>> Cheers,
>>>>     Bruce
>>>> On Wed, 16 Apr 2008, Gerry Creager wrote:
>>>>> We've used AoE (CoRAID hardware) with pretty good success (modulo one 
>>>>> RAID shelf fire that was caused by a manufacturing defect and dealt with 
>>>>> promptly by CoRAID).  We've had some reliability issues with Areca cards 
>>>>> but no data corruption on the systems we've built that way.
>>>>> gerry
>>>>> Bruce Allen wrote:
>>>>>> Hi Xavier,
>>>>>>>>>> PPS: We've also been doing some experiments with putting 
>>>>>>>>>> OpenSolaris+ZFS on some of our generic (Supermicro + Areca) 16-disk 
>>>>>>>>>> RAID systems, which were originally intended to run Linux.
>>>>>>>>>  I think that DESY proved some data corruption with such 
>>>>>>>>> configuration, so they switched to OpenSolaris+ZFS.
>>>>>>>> I'm confused.  I am also talking about OpenSolaris+ZFS.  What did 
>>>>>>>> DESY try, and what did they switch to?
>>>>>>> Sorry, I am indeed not clear. As far as I know, DESY found data 
>>>>>>> corruption using Linux and Areca cards. They moved from linux to 
>>>>>>> OpenSolaris and ZFS, avoiding other corruption. This has been 
>>>>>>> discussed in HEPiX storage workgroup. However, I can not speak on 
>>>>>>> their behalf at all. I'll try to get you in touch with someone more 
>>>>>>> aware of this issue, as my statements lack of figures.
>>>>>> I think that would be very interesting to the entire Beowulf mailing 
>>>>>> list, so please suggest that they respond to the entire group, not just 
>>>>>> to me personally.  Here is an LKML thread about silent data corruption:
>>>>>> http://kerneltrap.org/mailarchive/linux-kernel/2007/9/10/191697
>>>>>> So far we have not seen any signs of data corruption on Linux+Areca 
>>>>>> systems (and our data files carry both internal and external checksums, 
>>>>>> so we would be sensitive to this).
>>>>>> Cheers,
>>>>>>     Bruce
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