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Sharing a SCSI drive between two computers

Posted on 2006-04-27
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Can you share a SCSI drive between two computers?

If I have a controller in each machine with a different controller address, can I connect a SCSI cable from one controler to the next, and than to the SCSI drive, and than be able to access the drive from both computers?

If so, can this also be done with a RAID controller?
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Question by:Axter
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Lee W, MVP earned 800 total points
ID: 16559604
Strictly speaking, yes, you can.  But this should only be done when configuring a Windows cluster.  If you do this without clustering, you will corrupt the disk because two computers cannot have exclusive access to it at the same time.  The cluster service mitigates this.

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by:Duncan Meyers
Duncan Meyers earned 800 total points
ID: 16559845
>If I have a controller in each machine with a different controller address, can I connect a SCSI cable from one controler to the next, and than to the SCSI drive, and than be able to access the drive from both computers?

Yes, absolutely. You need to ensure that both ends of teh SCSI bus are properly terminated and that you can change the SCSI address of one of the SCSI controllers.

>If so, can this also be done with a RAID controller?
Yes - sam comments apply.

As leew says, you must have some mechanism to stop two systems scribbling all over each other's data. Clustering software provides that mechanism, as does VMware's ESX Server.
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by:Axter
ID: 16561005
Do you know of any cheaply priced clustering software?
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by:Renato Montenegro Rustici
ID: 16561409
unfortulately, Linux ...
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by:Duncan Meyers
Duncan Meyers earned 800 total points
ID: 16561678
Yep, Linux is it:
http://www.redhat.com/docs/manuals/csgfs/browse/rh-cs-en/index.html
http://www.scyld.com/ ....

W2K3 Enterprise or Veritas Cluster Server, Oracle RAC and so on you pay $$$ for.

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by:Axter
ID: 16563859
>>W2K3 Enterprise

I just found out from a coworker that W2K3 Enterprise comes with Windows 2003 Adv Server, which I happen to have three lic copies of.

So it looks like I should be able to set this up.

However, I'm not sure about one thing.
One of the SCSI controlers I have is a RAID contoller with three SCSI sets of controllers built into one.
For the RAID to work efficiently do I have to connect each SCSI drive to each connection, or can I connect all three SCSI drives to one SCSI cable?

If I connect it to each connection, I'm not sure if I would still be able to access all three SCSI drives from the secondary computer.
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by:Axter
ID: 16563863
Can you mix W2K3 Enterprise with a Linux cluster?
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by:Lee W, MVP
Lee W, MVP earned 800 total points
ID: 16563972
What are you trying to do?  Is this for a production environment?  Is this to learn and experiment?  What?  There are two primary types of clusters - Compute Clusters and High Availability clusters.  Linux clusters can do both, but USUALLY are used for Compute clusters.  Windows clusters can only do High Availability and Microsoft is WORKING on a compute cluster, but it's not been officially released yet.

You CANNOT mix Linux and Windows clusters.  Microsoft doesn't like to admit Linux exists and they certainly won't make Windows compatible with a Linux cluster (frankly, a high availability cluster wouldn't make sense to be cross platform compatible).

There is no such thing as Windows 2003 Advanced Server - There is only Web, Standard, Enterprise, and Data Center.  Windows 2000 Server came in an Advanced Server version - which is essentially Enterprise Server.

If you are building a cluster for a production environment, you DO NOT want to use the hardware you have without first checking if it's on the hardware compatibility list (HCL).  If it's not, forget clustering OR buy compatible equipment.  

If you're just playing, then go ahead and play - I clustered to systems with a couple of Adaptec 2920 Controllers and an external SCSI enclosure.  When I tried it again a few years later using 2940 controllers, it worked for a couple of hours then failed and I couldn't get it to work again (2940 controllers are NOT on the HCL).

> One of the SCSI controlers I have is a RAID contoller with three SCSI sets of controllers built into one.
> For the RAID to work efficiently do I have to connect each SCSI drive to each connection, or can I
> connect all three SCSI drives to one SCSI cable?

I have never heard of a triple channel card - you either have a single channel, dual channel, or quad channel card.  Do you mean there are three connectors on the controller?  If so, that doesn't mean you have 3 controllers, it just means you have three connectors and POSSIBLY two controllers, depending on the card.

Controllers usually seem to be setup to use one channel or the other, per set of SCSI disks.   But some RAID controllers can span channels so you COULD possibly use both.
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by:Axter
ID: 16564127
>>I have never heard of a triple channel card -

I have a Adaptec AAA-132/133 controller, and all the links I've viewed shows it as a 3-channel card.
http://cgi.ebay.com/Adaptec-AAA-133U2-3-Channel-Ultra2-SCSI-RAID-W-16Mb_W0QQitemZ8802064287QQcategoryZ39968QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://gooddealcanada.com/pc_detail.php3?id=1352222

>>What are you trying to do?  Is this for a production environment?  Is this to learn and experiment?  What?
I want to use them as secondary drives for testing builds.
The builds I perfrom have over 10,000 source files, and take a very long time to perform.  On each build, the source code is pulled from CVS before the build, so the drives will not contian any important data.
I'm also doing it for learning purposes.
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by:IPKON_Networks
IPKON_Networks earned 400 total points
ID: 16577413
I'm not sure what your objective is here. Are you trying to achive a cluster and share the same piece of data between to computers or are you just saving on disk space !!!

A cluster is useful if you are planning to have computer A do some work and then Computer B take over if computer A fails, as an example. However, surely you would be better off simply sharing the volume from one computer to another and use the network for data tranfers?

If you plan to boot both computers from the same disk then you will have all sorts of issues and again, I'm confused why you want to do this.

Can you help me out what you are trying to achieve?

Many thanks
Barny
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by:Axter
ID: 16577462
>>If you plan to boot both computers from the same disk then you will have all sorts of issues and again, I'm confused why you want to do this.

No, I don't plan to do this.  This will be a third, or forth drive on each machine.

>>However, surely you would be better off simply sharing the volume from one computer to another and use the network for data tranfers?

I also want to test a program during fail-overs, using clusters.
I'm mostly going to be using the drives for doing builds, but I also want to use them for testing and debugging a program I have that's suppose to work in clusters.
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