SCSI Disk/Controller advice please

Justin Knierim lfs.matrix at gmail.com
Sat Oct 30 14:11:35 PDT 2004


Hi,

I will take a whack at a few of the questions, but I am by no means an expert.

> I'm looking for advice on these: wich scsi controller should I buy?

I have only used adaptec, but there are many other good brands as
well.  LSI I have also heard of.

> Software or Hardware RAID-1? Wich disk brand? (I'm getting a couple of
> 36GB, it is more than enough space for my setup)

Hardware raid controllers are more expensive usually.  It all depends
on what you are using the server for.  If you need absolutely the
fastest possible disks and everything fast fast fast, then a hardware
raid might be more trouble-free.  If not, software raid is also good:
http://www.tldp.org/HOWTO/Software-RAID-HOWTO.html

> What happens/How do we proceed if 1 disk fails (how do we know it, how do we replace/resync them?)

With both hardware and software raid, when the hardware/software
recognizes that a disk was replaced, should rebuild the drive.

> This server can be shutdown for maintenance at off-work hours, so I
> don't need any hot-plugging capability.. (this is a controller feature,
> right?)

As far as I understand, no.  Most scsi controllers you can command to
shutdown/disconnect the drive, and then it can be hot-swapped.  Most
"hot-swappable" or drives in drive trays use the scsi SCA connectors,
which are 80 pin with scsi and power built in.  The normal 68 pin is
just scsi, and is if you hooked the drive up with a cable.  There are
adapters to switch between the types, but a 68 pin drive with an SCA
adapter would normally not fit in a drive tray (too long).
 
> I'm quite confused about all the SCSI variations..

Yeah, there are a lot of them.  Here is a bit of info:
http://en.wikipedia.org/wiki/SCSI
 
> This is what I've found so far are somewhat like this:

Again, 80 pin SCA is only needed for hot-swap trays.  If they can be
replaced as you said "after work hours", then you can get the
(normally cheaper) 68 pin drives.  The RPM is dependant upon use.  A
10K drive is plenty fast, but if you need it that much faster, get
15K.  For brands, it is personal choice.  IBM I don't trust because of
the last IDE drive I had with them (replaced 10!!! times in warranty
in 1 year), but maxtor, fujitsu, seagate are mostly good.  My little
workstation uses a fujitsu, and besides being noisy, has worked great
running 24/7 the last 6 years.  ;)

> - Controllers
> Several Adaptec SCSI Cards from 200 to 400 EUR, wich can have:
>   - 32 or 64bit
>   - 160MB or Ultra320
>   - Raid (or not, when they say nothing.. I think) (the RAID ones start
> at 400 EUR and I've seen up to 950 EUR)

What does your server motherboard have?  If you have 64bit PCI slots,
and really need the speed, then 64bit.  The same with Ultra160 or 320.
 Scsi drives are backwards-compatible (to a point) and so if you do
not need the huge speed, 160 might also be ok.

> I'm confused... none of the descriptions of the Adaptec controller I've
> seen state the connectors (68/80 pins)... now add more controller to the
> mess:

Any controller that can do ultra160, ultra320 or even normal LVD, will
have 68 pin connectors.  If you would buy SCA drives, you would need
an adapter or a backplane (for server hot-swap setups) to adapt it to
68 pin cable anyways.  The controllers could also have 50 pin
connectors, which is that wide flat cable (like a fat IDE cable) that
is used for some cdroms, etc.
 
> Tekram PCI DC395UW   - 56 EUR

Couldn't help you, never heard of Tekram, but that does not mean they
aren't good.

> Damn... Really confused... Please confirm these toughs also:
> UltraWideSCSI = 68 pin ... What is "2", "3" or "4" ?!? These seem
> "similar" to ATA 66/100/133 - the bus speed, is that it?
> So, what's SCA? None of these controllers says SCA...

Check the wikipedia link above, and my SCA description above.  ;)

> Ps: I supose getting a SCSI crontroller built-in on the motherboard is
> stupid? Those are low-value/performance controllers?

Depends.  They are normally decent controllers, but don't normally
have hardware raid, if that is what you want.

-- 
Justin R. Knierim
lfs dot matrix at gmail dot com



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