persistent storage hardware: recommendations, comments, and opinions please

[dman <dsh8290@rit.edu>]

First my current setup:
    10GB Maxtor IDE disk
        Size  Used Avail Use% Mounted on
        5.6G  5.1G  271M  96% /
        4.0G  2.5G  1.3G  64% /home
        125M   40k  124M   1% /tmp  (tmpfs, not on-disk)

I want to buy another disk to augment this.  There's not enough room
on this one for my music _and_ an OS (and working files -- homework,
etc).

I stopped by the local computer shops and took some notes on the
available hardware.  I'd like some comments, recommendations,
opinions, and other info you may have.  (prices in USD)


Disks :

Western Digital WD400BBRTL
    40GB, 7200 rpm, Ultra ATA 100, 8.9 ms seek time, 2MB buffer, $130

Western Digital WD180ABRTL-120
    18GB, 5400 rpm, Ultra ATA 100, 12.0 ms seek time, 2MB buffer, $80

Samsung SV4002H  (looks like a used disk)
    40GB, 54000 rpm, ATA 100, $110

The one shop also had 2 Maxtor disks, but I'm not sure I want another
one of them.


Can someone provide a comparison of Ultra ATA 100 and SCSI?  Which is
faster and/or more reliable?  


Controllers :

Adaptec SCSI Card 2906
    7 devices, non-bootable, 10 MBps transfer, $63
    SCSI 1, SCSI 2, Fast SCSI 2

Adaptec ATA RAID 1200A
    2 ATA/100 channels, RAID 0 1 0/1 JBOD, bootable, $100

CompUSA (Silicon Image Sil0649CL160)
    Ultra ATA 100, 2 channel, ACPI, $30


Does RAID restrict the combination of disks I can have?  IIRC RAID 0
is no redundancy, and RAID 1 is simply maintaining two copies on
separate disks.  If so, then wouldn't both disks need to be the same
size?

TIA,
-D

-- 

The truly righteous man attains life,
but he who pursues evil goes to his death.
        Proverbs 11:19