[BBLISA] RE: storevault / netapp

Edward Ned Harvey bblisa2 at nedharvey.com
Wed Feb 27 22:29:28 EST 2008

> 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.

This is really interesting.  I have noticed bit errors occasionally, and I
am unusually paranoid of such a thing.  It's about 50x more common in my
personal experience, with optical media than magnetic.  And almost never on
a healthy ethernet.  I do checksum and validate things with almost obsessive
compulsion.  Especially installation & backup images.

That being said, I didn't know ZFS checksums on the fly.  I can only assume
this hurts performance, likewise if there's a lack of hardware caching, but
I also habitually use iozone to benchmark my raid systems.  Typically dell
sata disks with caching raid 5 controller.

I haven't googled for iozone results on ZFS systems, but if anyone here has
any such results, I'd be interested in comparing.

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