Database performance, deadlocks

Hi all,
I'm trying to settle a discussion I'm having internally.
If you have a database server with high I/O wait, continously (over 60% for extended periods of time) and that server has only one disk mirrored for the whole system. (database is way to big to just cache in memory). I'm arguing that we need to improve the disk subsystem as having only one disk for everything (including archived logs) is a terrible setup.
However we have intermitent deadlocks that show up. Yesterday over a 5 hour period of slow performance we had 1 deadlock. Now I ask, is it possibly for deadlocks to put I/O wait and excessive load on the server? (there are many threads into the database and this deadlock impacted 2 of them out of 70).
I'm having a hard time because I have a non-technical person making the decision to buy hardware and I have this lone dissenter saying that all the performance problems are because of a deadlock....
(read one single deadlock over the course of a day).
thx

What database version and OS are you on??9.2.0.5, Redhat AS 4 update 4
What is the size of SGA??400M, hit ratio not an issue
How much RAM do u have on that box??4G
How many concurrent connection do u have on that server??70ish
Oh believe me I'm pretty sure I know what the problem is. What I'm trying to discount is that a single deadlock can cause performance problems over a 5 hour period of time.
I don't see any waiters, I don't see anything to indicate to me anything other then it's the the disk subsystem that should be looked at first.
However, I'm trying to see if there is any possibility that a deadlock can cause the level of performance degradation and i/o wait that I see. I know that if the whole system deadlocked up that that would be bad but what I've seen is a single deadlock that involved 2 connections total.
thx

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