LUNs?

[SuperDave1685]

Hi there guys. I was wondering if someone could help explain the concept of LUNs (Logical Unit Numbers) and their role in Cluster Shared Volumes? I'm kind of at a loss here to grasp the concept.

 

[Robert17]

This won't be the best answer you'll get but it should get you started.

The LUN was based in the old days (may still be, just don't know) off the SCSI ID address whether it was 8-bit or 16-bit addressing. Daisy chaining the drives off a single controller meant sharing of the address volumes' ID dependent on how many logical units were chained.

Now it's someone else's turn.......

 

[SuperDave1685]

Thanks for the insight Robert. I've managed to find a few links that kind of help.

http://blogs.msdn.com/b/clustering/archive/2009/03/02/9453288.aspx

That one is a particularly good link. Having to learn all of this stuff take a lot of brain power for sure

 

[Robert17]

Yeah, CSVs. I've got some catching up to do too !

 

[Janus67]

I can't give you a perfect answer, but one idea if you want to branch out of OCF may be to try posting to http://www.reddit.com/r/explainlikeimfive/

There are generally some really good explanations in that subreddit.

 

[Noshei]

So a LUN is a sort of way to identify the storage that is allocated to a device. It is a very abstract identifier when viewed at a high level and only has relevance when put into context.

There can also be multiple different LUN designations for the same storage allocation, depending which side of the connection you are looking at (Array side LUN and device side LUN).

LUN is also used as a term to denote a storage allocation, ie "Can you assign a new 1TB LUN to my server."

So like I said LUN can be a very abstract term without context, so do you have more information on what exactly you are wanting to know about it?

 

[gangaskan]

So a LUN is a sort of way to identify the storage that is allocated to a device. It is a very abstract identifier when viewed at a high level and only has relevance when put into context.

There can also be multiple different LUN designations for the same storage allocation, depending which side of the connection you are looking at (Array side LUN and device side LUN).

LUN is also used as a term to denote a storage allocation, ie "Can you assign a new 1TB LUN to my server."

So like I said LUN can be a very abstract term without context, so do you have more information on what exactly you are wanting to know about it?

LUN's are now used in ISCSI communication between a NAS that supports ISCSI Target(s) and the PC Requesting a data connection.


you can make a LUN about any way but it represents almost a DNS address in a sense, it also carries and identifies what LUN you want to attempt to connect too as most storage array's will not just put a massive disk on one unit.

a LUN will normally have a hostname, date, and target name associated with it.

for example, a lun may be looked at as

iqn.2006-01.com.openfiler:tsn.343421488512454

note the iqn, date, domain, and target identifiers (this is not a real LUN, just an example of what one "might" be)



think of it as carving out a dedicated space for a device, server, etc .... about anything you can think of. you can have multipule pc's connect to one LUN to share, which is great for VMWare to do DRS and HA for example.

 

[SuperDave1685]

Thanks gangaskan That's kind of what I picked up on. It kinda is an abstract concept for sure. I was doing some labs yesterday with FreeNAS and VirtualBox setting up iSCSI targets, so that helped solidify the idea

 

[gangaskan]

Thanks gangaskan That's kind of what I picked up on. It kinda is an abstract concept for sure. I was doing some labs yesterday with FreeNAS and VirtualBox setting up iSCSI targets, so that helped solidify the idea

no problem