[geeks] Solaris 10 / OpenSolaris bits to be in next version of OSX

[Charles Shannon Hendrix]

Thu, 10 Aug 2006 @ 21:18 +1000, Scott Howard said:

> Create a mirror using your favourite volume manager/filesystem
> combination, mount it, and start some IO.
> 
> Then "dd" over one side of the mirror with something like
> dd if=/dev/zero of=/dev/rdsk/c2t2d2s2 bs=1048576 count=5

So I'll dd over the data and its copy.  

Down goes ZFS.

ZFS is nice, assuming it actually does what it claims, but I think it
makes some tradeoffs that aren't so good, and I'm still not sure it
doesn't do bad things as well.

For example, what I said earlier about how it handles its disagreements
with the hardware.  

Also, one nit in your example: several OS would prevent you from raw dd
write to a mounted filesystem.

> With any other FS/VM I'm aware of this would have toasted the filesystem
> so badly that it would have needed backups to fix, but in this case ZFS
> detected the errors and corrected them.  There were NO disk errors
> reported as the array didn't know anything was wrong.  There were no
> disk CRC errors reported as the data on the disk was OK, just much of
> it was stale.  A perfect example of Silent Data Corruption.

That sounds good.

I think a lot of what is being said about ZFS here is incorrect, and is
part of the reason why some of us worry about it.

However, just because the above worked, isn't completely convincing.

I've seen userland filesystems or even applications do the same thing.


-- 
shannon "AT" widomaker.com -- ["Meddle not in the affairs of Wizards, for
thou art crunchy, and taste good with ketchup." -- unknown]