Two machines sharing a SCSI RAID

Hi,
You'd mentioned that you were told a week ago that this setup would work. Can you post the link to that question here? From what you described above, I don't see how Windows 2000 would work correctly like that.

Cheers!
~Sean

What you are describing is the beginning of a cluster env. Network load balancig may have been set for these to see the same drive and that may be the problem. also if you are hooking bothe servers to one scsi device with scsi cables, the normal routine is to use "Y" cables with terminators, is this the case??
1. what EXACTLY are the operating systems??
2. are you running load balancing??
3. are you running a cluster env??
4. what network cards do you have (yes it makes a diff)
5. what arethe scsi cards and connectors and terminators??

Let us know and we can help you...........

If I save a file on one computer, then go to the other computer and run check disk on it (properties, tools, check now, automatically fix file system errors, start), then the other computer can see what the first computer saved.
But Check Disk changes the permissions to admin, system: full control - this folder only.

So it is possible to share files, but I need a "hands free" way of doing it.

I vaguely remember seeing an article at Microsoft?s web site, but I haven't found it again yet.

I fear you are attempting a configuration that isn't possible. I have never seen any SCSI device that gives you the capability to share the device between multiple computers.

Yes, the Data Silo has the capability to connect to multiple SCSI hosts. But in SCSI terminology a "host" refers to a SCSI controller, not a computer. I think the purpose of this is to give you some redundancy should one SCSI controller fail. This would also give you the capability of splitting the drives in the enclosure into multiple arrays. I don't think it is meant to allow you to connect multiple computers to the same array.

To make sure, you need to talk to the StorCase technical support people.

If the servers are connected to a network, all you need to do is share the "disk" that represents the array from the ONE server the array is connected to. Then, all computers that connect to the network can "see" and access the datat on the array.

Hi,

that what you try ist not possible !
Their is no clustering, thats in fact what you want, on filesystem!! In fact you may see the file from both machines, but in the moment you try to open it, the Filesystem will crash.
I know that Vertiasis working on a Clustering Filesystem, but in the moment their is no such thing.

regards

Frobo

We've had the similar situation some 4 years ago, it was well before Win2000 and distributed RAID controllers, and solution was to change the drive letter (say from G: to I:) and then second machine will see files that first computer wrote. Disgusting thing. Now I propose you to install the most fresh drivers (from web site) of that RAID controller to both stations, and if that won't help, well, go for manufacturer's support.

I've called StoreCase Technologies to ask them about this, and the representative said I will be called back when the tech. gets off another line.

Ok, I also have not heard of this sharing SCSI technology, so I cannot comment on it.
Now, if you had a SAN device with virtual LUNs carved out of it, I believe that you can have a single LUN be seen by multiple Win2K servers. The LUN is just a fixed amount of drive space, and it can be formatted as a drive (say, for example, yo make LUN3 a 4GB drive). You then have the Win2K servers connect to the SAN via fiber channel connections (using a fiber switch from companies like Brocade), and tell each server to connect to LUN3. The servers then see LUN3 as a new disk drive. You then have each server assign its own drive letter to the LUN, but don't format it!
Voila! Multiple servers sharing the same drive space that is on a remote system, and each server sees the drive space as a new local hard disk. Very cool, actually!

But, this is not your situation. I just wanted to explain how it could be possible.

I don't see how this setup will ever work.

You are working with two differenct File Allocation Tables. When machine #1 writes file it updates it File Allocation Table. Machine #2 File Allocation Table is not updated until you run chkdsk. You will need special software to keep respective File Allocation Tables in sync.

The StoreCase representative said that he thought it would work if I would get volume management software.
He suggested
ATTO Accelware at attotech.com and
Kayo at www.sanbolic.com/kayo.htm
Has anyone used them?

YOu need to look into getting a management suite. Veritas is a very good manager. There is also a SAN manufacture that I believe is giving up its management software, they are called Zygotech. The problem is Win2000 is just not able to do what you want in this situation, but you have already figured it out =)

check the gpo to see if its well configured its sounds like files systems on there the user doesn't have the right

Is there a write cache enabled on the drive? It could be the data has not been written to the disk and running chkdsk flushes the cache making the file appear.

I am not too sure how NTFS or if NTFS uses a File Allocation Table (FAT) if it does it could be possible that this is also being cached. So an update to the FAT on one machine will not reach the disk until the cache (or buffer) is flushed.

This is a little far fetched as the caches should be periodically flushed anyway so we are only talking about a few seconds before the data is actually written to disk.

That said I would still investigate it.

I am a little confused about what you are trying to acheive though. One machine must be the "owner" of the drive. This is how network shares work and how multiple clients can connect to the same share without conflict.

What you are trying to setup is where both machines believe they own/control the disk. We have a number of RAID boxes here all with two SCSI interfaces for hosts so that we can cluster the boxes. When you cluster two machines you specify a that drives (resources) are owned by specific nodes. This allows the cluster service to co-ordinate writes/reads etc.

You are lacking this form of co-ordination. Neither box will be aware of the other and WILL conflict. For example, what if each box tries to create a file in the same location on disk at the same time? Who knows who will win. The result will be a mess of a file (if your lucky, unlucky = no more data).

You could probably get away with this kind of setup if one machine writes files and the other is just reading. In that case we must make sure no data is being cached at all and it is all written to disk straight away. Thiswill degrade performance somewhat.

I hope that helps.

FILE METADATA 101

If you are running Fat or Fat32 it is called a File Allocation Table (FAT). If you are running NTFS it is called a Master File Table (MFT).

These "files" are used to keep track of the locations on your hard drive that nbormalfiles are stored. Any new files are entered here and written to the disk. Any deleted files just have their entry erased from this "file" the actual data is still there but is overwritten when ever that spaced is needed. This is how alot of those dleted file apps work. They actually scan the drive and create their own FAT or MFT "file".

ON TO YOUR QUESTION

Based on what I have told you above, what you are looking to do is not possible under standard Windows - any version. This is because each server or OS has it's own FAT or MFT for that drive. When you update the file on one, the other servers FAT or MFT is not updated as they are not sharing any kind of monitoring app that maintains this info. This is why a number of people have been suggesting a third party storage management or volume management system. I am surprised that this StoreCase Technologies does not provide their own volume manager solution for this. This is the norm as the application is written for the hardware. It doen not tend to be a generic application. In my exoerience it has always been very vendor specific.

An alternative solution would be to schedule a checkdisk followed by an ACL script to run every so often.

If you need help with this script,you can email me.

Personally, I would start looking for a new vendor to provide this solution.

Good luck

Dear Davidag..

Your tech support is correct...

Win2K systems can share a scsi bus (raid or otherwise) as long as the hardware conforms do SCSI rules. However each system will act independantly on the disks, this behaviour is quite normal and you MUST use some form of volume management software such as Veritas or Cluster Server software to allow shared access and security to the disk.

Other problems with this configuration have to do with the way each system will cache access to the disk that can cause corruption unless properly handled by shared software.

Also note that the "everyone" identifier is different at local and domain level and will look "foreign" to both systems unless both are applied at the domain level.

I hope this helps

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