7.0-Release and 3ware 9550SXU w/BBU - horrible write performance

[alan bryan]

--- alan bryan <alan.bryan at yahoo.com> wrote:

> 
> --- alan bryan <alan.bryan at yahoo.com> wrote:
> 
> > Hi,
> > 
> > I've got a new server with a 3ware 9550SXU with
> the
> > Battery.  I am using FreeBSD 7.0-Release (tried
> both
> > 4BSD and ULE) using AMD64 and the 3ware
> performance
> > for writes is just plain horrible.  Something is
> > obviously wrong but I'm not sure what.
> > 
> > I've got a 4 disk RAID 10 array.
> > 
> > According to 3dm2 the cache is on.  I even tried
> > setting The StorSave preference to "Performance"
> > with
> > no real benefit.  There seems to be something
> really
> > wrong with disk performance. 


So, all of this seems to be due to the Battery unit. 
What seems to be happening is that if the battery
isn't fully charged the write cache get disabled.

So, when I was testing and removing the card, changing
cabling, etc... with the server powered off the
battery would get ever so slightly discharged and then
when booting back up the server has the cache off
until it gets topped back up again.  Thus, I was
seeing weird inconsistent results all over the place.

I had to move the BBU and disconnected it for a few
minutes and then turned the server back on.  When it
came back up 3dm2 reporting that the BBU was charging
and that write cache was off.  Once recharged (15 min
or so) the cache was turned back on.

This could be really bad in a loaded server if you
have to down it for a few min service window and then
boot back up and the write cache is then off.  I found
that I could log into 3dm2 and change the StorSave
profile to "Performance" which would then enable the
cache again (it ignores whether you have the BBU). 
Then once the battery is charged you can go back to
"Balanced" profile.

Guess the lesson learned is make sure the server has
been powered up for 24hrs and battery fully charged
before doing any tests against this 3ware card.


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