Single iSCSI target connected from multiple iSCSI initiators

[weslowsk]

Hi,

I'm getting mixed messages from a QNAP article and QNAP support for the iSCSI setup that I'm interested in using and I'm looking for the community's advice.

This article: https://www.qnap.com/en/how-to/tutorial ... turbo-nas/

suggests that I should be able to connect more than one iSCSI initiator to a single iSCSI target, in a non-clustered environment, safely, as long as I use the correct LUN masking policies.

I want to see if anyone has done this before and, if so, what their experience was. My first attempt didn't succeed so I reached out to QNAP support. QNAP support and I don't seem to be interpreting the article the same way so they haven't been able to help me yet.

Any advice/experience on this out there?

[storageman]

Why do you want this?
You will get corruption if you do this.
Even if you set the other ISCSI host to read only, any changes will not be populated over immediately, lags can occur.
Use shares if you want to share volume usage.

[weslowsk]

Why do you want this?

1. Because the documentation says I can
2. As an alternative to using shares
3. To get more low-level control from the client point of view. From the read-write client, I can treat it like a regular disk and format it however I like. From the read-only client, I can treat it like a read-only disk. In this scenario, I can write to it from one client and the other client is responsible for reading it and, say, backing up the files on it without the possibility of overwriting (corrupting) any of the files.
4. Testing the performance of iSCSI vs. SMB from a client point of view

The article must have been written because somebody else wanted to access the same target from multiple clients in a non-clustered environment. Prior to that, the functionality (LUN masking) was added to QNAP just so that somebody could do this very thing.

You will get corruption if you do this.

The article specifically says that you can do this safely, which I interpret to mean without corruption, if you employ QNAP iSCSI Advanced ACL. Am I mis-reading the article? Have you actually tested this and proved that it causes corruption?

Even if you set the other ISCSI host to read only, any changes will not be populated over immediately, lags can occur.

I'm fine with that.

Use shares if you want to share volume usage.

I already use shares for other purposes and I'm aware of it. This approach with iSCSI seems to be another way of sharing data/volumes.

[storageman]

To get your terms straight the target is an ISCSI link to the NAS, it is not the LUN.
A target can have one or more LUNs, and you can have more than one target, a LUN can only have one and only one target.
Again if you share a LUN in a non-clustered environment in read/write mode to more than one host you will get data corruption.
On your head be it!