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Background:

I have two SANs (Dell Equallogic PS6100E, though not necessarily an eql. question). I have a NAS that connects to them (FS7600). That NAS is on the regular network lan, but has it's storage on the SAN.

I can make the SANs one giant NAS reserve (Dell parlance), so that my entire SAN is NAS space, assuming I made one giant array/member to begin with. This means no separate pool or members separate from the big reserve.

Question:

Why might I want to provision block iSCSI targets? All the file systems are the same, the RAID configs will always be the same and so on. Are there special applications where iSCSI applies; even homogeneous OS and file systems? When might I require iSCSI?

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johnny
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    I've reworded you question a bit. As you've found, an accusatory tone questioning the relevance of a widely deployed technology tends to favored. I hope you don't mind. Unfortunately the question boils down to "Enumerate all the applications of iSCSI", which is overly broad and not well suited to a Q&A site. If you're still curious as to the fundamental differences between file system sharing and block storage sharing there are quite a few sites that enumerate the essential applications for NAS and SAN appliances, and a [chat] full of lazy SysAdmins. – Chris S Mar 04 '13 at 21:09

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Clustered file systems (such as OCFS2) require block-based sharing (such as iSCSI, FC, FCoE etc.) so that they can manage locking on a distributed basis, this can't be done with NAS protocols which have a smaller functional capability list.

Chopper3
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Yeah - if you ever have to present block storage to something, as opposed to serving it up over NFS or SMB. That's kind of the definition of the difference between NAS and SAN - they do different things and fit different needs. And Sven's right - how could we know (from your question) what you might require now or in the future?

mfinni
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  • You misunderstand. I do not expect you do know what *I* need. It is simply a manner of speaking. That is, when does that need arise, not if I really need it. It is a conceptual question. – johnny Mar 04 '13 at 18:47