Is it safe to run gjournal on aac-based system (BIO_FLUSH)?

[Toomas Aas]

Hello!

I'm planning to install FreeBSD 8.1 on a system which has Adaptec  
4805SAS RAID controller (using aac driver). I'd like to use gjournal  
for the data partition, but I have some doubts regarding the (lack of)  
BIO_FLUSH feature.

I have another system with FreeBSD 7.3 and a different aac-based  
controller where I've been using gjournal for 3 years. Every time the  
system boots, it prints this warning:
GEOM_JOURNAL: BIO_FLUSH not supported by aacd1s2.

I understand that lack of BIO_FLUSH support means that data cannot be  
safely flushed to disk and that might cause corruption in case of  
sudden power loss. Is that correct? Anyway, since this system has  
battery-backed write cache, I'm not too worried.

But on the system where I'm about to install now, the controller  
doesn't have a battery for its cache. Hence my question - does the aac  
driver on FreeBSD 8.1 still not support BIO_FLUSH? If so, I should  
probably avoid using gmirror on this system?

-- 
Toomas Aas