Re: disks for redo logs
Date: Sun, 15 Feb 2009 16:42:17 -0800 (PST)
Message-ID: <2a4fabb5-fae5-4f26-941d-dccc8b4433ed_at_e6g2000vbe.googlegroups.com>
On Feb 11, 2:26 pm, joel garry <joel-ga..._at_home.com> wrote:
snip
> 10.2.0.4 (and I would guess above) check out the ${ORACLE_SID}
> _lgwr*trc trace files, it spits out a message whenever log writes take
> more than .5 seconds or something, compare to your performance
> monitoring. I was a bit surprised when I first noticed what's in
> those traces, haven't quite figured out how to translate that for
> management. The surprising part was the size of writes versus the
> waits - apparently quite unrelated. Which I guess makes sense if the
> waits are caused by other things than the log writes.
>
> I used to think having different volume groups would help, but I've
> been disabused of that notion. Now I don't understand it at all. SAN
> cache makes it all strange, too.
IO hiccups and "strange unrelated spikes" in IO response time in a SAN environment involves some aspect that Dante wrote about as far as I know. No knowledgeable SAN admin ever admits to knowing anything ( well rarely anyways ) relevant.
> But hey, if users aren't complaining, everything is peachy. Right?
If it is log writes from a commit or rollback then any other transactions ( if any ) involved in any concurrency situations will be impacted ... but you know that already eh? Received on Sun Feb 15 2009 - 18:42:17 CST