[NTLUG:Discuss] Disk performance.

[Steve Baker]

Greg Hewett wrote:

> There are many areas that affect the I/O of you drives.  Your pci bus is
> shared, so if you are sharing the bus with other I/O intensive devices, then
> there will be problems.

I'll be hitting a 100baseT adaptor pretty hard - but nothing else should
be going on anywhere in the system.  This is on a local network that
doesn't connect to the outside world at all.
 
> I think that you need to go to SCSI.  SCSI is said to be able to push 60-70
> Mbytes/second.  I do not think you can get close to that with the type of
> reads that you are doing and with one spindle.  A raid array would really help
> you get the most performance out of your SCSI bus because your data would be
> on several spindles.

OK - So I shouldn't need multiple SCSI busses for bandwidth reasons.

Since I need about 0.6 terabytes of disk space in the extreme case,
*twelve* 50Gb drives would be about right.

I also need to configure systems which need much less capacity than that - where
a single 50Gb drive would suffice - but I still need the speed.

> Where to go from here?  When suggesting a solution I have a co-worker that
> says pick 2... Good, Fast, or Cheap.  This all depends on the importance of
> the data.

The integrity of the data isn't critical.  It'll hardly ever change during the
lifetime of the machine - and it'll be archived elsewhere for backup purposes
- I could even use an array of DVD-ROM drives if I thought it would work!

>   Raid Array - not cheap
>   Single SCSI disk - not good
>   Software Raid - not fast.

Well, it's certainly not going to be cheap just because of the sheer volume
of storage that I need - so good and fast are two I'd pick. 

Is a hardware RAID setup expensive because of the controller - or because
of the number of hard drives?   Since I need a LOT of drives just to get
the capacity up high enough - the actual RAID controller might not be a
big deal.

How 'not cheap' is RAID?

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