# disk write caching opinions



## bigearsbilly (Oct 7, 2009)

I was reading Absolute FreeBSD (good book)
and there was a mention that data is a lot safer 
with disk write caching off. i.e.
*hw.ata.wc=0*

so i tried it and it turned my dual core AMD64 into an 8086
when I did any disk writes. 
(I copied a 4G file from a USB disk to /usr)
the write took about 900s opposed to 227s
all my desktop slowed down as to become unusable.

so I turned it back on.
So, my question is do you think there is an appreciable increase
in danger of data loss? 

i.e any one experienced it.


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## SirDice (Oct 7, 2009)

Turning write caching off is pretty detrimental to performance as you have noticed. IMO it's the filesystem's job not to make a mess of it even when the power goes out. AFAIK UFS2 does do a decent job but ZFS is a lot better in this respect thought.


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## aragon (Oct 7, 2009)

You can also enable gjournal(8) on your UFS file systems.  Ultimately though, if you want assurance you should invest in a UPS and do backups.


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