log file dilemma! share disk with OS or Data file?

Generally speaking, If you have to pick a poision between sharing a disk
with Operating system drive or sharing a disk with Data file drive, which
one is the worse in terms of system performance?
Here is the scenerio: I have a mirrored drive where I put OS on c$ partition
and created another partition of d$. And we have 4 more drive left.
My options are:
1. Create RAID 5 volume from all 4 drives and put data and log file on that
volume. The advantage is that Bigger disk space usage but very bad on system
performance.
2. Create RAID5 volume from all 4 drive but put only Data file in that RAID
5 and put log file on d$ (The drive where OS files are).
3. Create Two RAID 1 drive and put data on first RAID and log on 2nd RAID.
This is best for performance but I loose lots of disk space.
I know no. 3 option is the best out of 3. But, if you have to choose between
no. 1 and 2, which would you prefer? and how bad the performance hit will be
if we compare no. 3 against no. 1 and no. 3 against no. 2?
I appreciate your answer. SQL SERVER 2005 SP2
I would say Option 2. Once the system is up and running there should not be
much access to the OS volume so the logs would not have too much contention.
This is assuming you don't have other issues that might cause problems like
excessive paging or another process writing a lot of data to the OS volume.
-jeff
"James" wrote:

> Generally speaking, If you have to pick a poision between sharing a disk
> with Operating system drive or sharing a disk with Data file drive, which
> one is the worse in terms of system performance?
> Here is the scenerio: I have a mirrored drive where I put OS on c$ partition
> and created another partition of d$. And we have 4 more drive left.
> My options are:
> 1. Create RAID 5 volume from all 4 drives and put data and log file on that
> volume. The advantage is that Bigger disk space usage but very bad on system
> performance.
> 2. Create RAID5 volume from all 4 drive but put only Data file in that RAID
> 5 and put log file on d$ (The drive where OS files are).
> 3. Create Two RAID 1 drive and put data on first RAID and log on 2nd RAID.
> This is best for performance but I loose lots of disk space.
> I know no. 3 option is the best out of 3. But, if you have to choose between
> no. 1 and 2, which would you prefer? and how bad the performance hit will be
> if we compare no. 3 against no. 1 and no. 3 against no. 2?
> I appreciate your answer. SQL SERVER 2005 SP2
>
>