[BBLISA] RE: storevault / netapp

[Peter Galvin]

Well, now you've gone and opened up a whole new can of worms. :-)

It is absolutely not the case that hardware RAID has across the board lower
risk of data corruption, with or without caching. Caching usually increases
speed, as you say.

Take a look at this article if you want to be scared about data corruption,
even when using hardware RAID:
http://storagemojo.com/2007/09/19/cerns-data-corruption-research/

Theoretically, ZFS has much better data integrity than other file systems /
volume managers / RAID controllers because it checksums all data and all
metadata, all the time. Nothing else (that I know of) does this.


--Peter

Blog: http://pbgalvin.wordpress.com
 


On 2/27/08 12:08 PM, "Edward Ned Harvey" <bblisa2 at nedharvey.com> wrote:

>> RAID can be implemented in hardware or software. Can't speak to all
>> hardware
>> RAID controllers, but NetApp does RAIDDP, and ZFS has RAIDZ2, both of
>> which
>> are double-parity-disk RAID (i.e. Survive 2 disk failures rather than
>> 1).
> 
> This is very interesting.  Is there any hardware controller that does the
> same?
> 
> I do think there's value in the hardware raid controller.  Guess what, we've
> all seen sometimes kernel crashes.  And if we had enabled write caching,
> we'd encounter FS corruption for whatever had not yet been written.  But
> with a caching raid card, with battery backup, you get all the performance
> benefit (if not more) with lower risk of data corruption.
> 
> The performance difference is most apparent when working on a zillion small
> files.  The most dramatic difference I've seen is when formatting the FS,
> because of course, that's such a sparse write operation.  To format 1Tb on
> my Dell, ext3, it took 40 minutes without write cache enabled on the raid
> card, and it took 40 seconds with the write cache enabled.
> 
> _______________________________________________
> bblisa mailing list
> bblisa at bblisa.org
> http://www.bblisa.org/mailman/listinfo/bblisa