[BBLISA] RE: storevault / netapp

[Peter Galvin]

Hey Edward, ZFS makes up for the performance loss due to checksumming by
using a lot of smart algorithms. In some places its faster than other file
systems / volume managers  RAID controllers and sometimes slower.  Sun is
working to improve performance (of course) with some interesting stuff in
the pipeline.


On 2/27/08 10:29 PM, "Edward Ned Harvey" <bblisa2 at nedharvey.com> wrote:

>> 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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--Peter

Blog: http://pbgalvin.wordpress.com