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I have looked around so much but still couldn't find a practical working answer/example about adding a new storage machine to the iscsi san network and instead increase storage capacity.

What I have found and done.

  • I found steps on how to install iscsi targets and inititors.

  • I also found procedures on how to access the storage.

  • And setup redundancy among-st all components.

what happens when I add a new iscsi storage from a new machine.?

The initiator/client see the new machine storage as an independent storage yet I intend to make it extend the size of the current storage.

But now I need serious help on how to make all of these iscsi devices show as one enormous storage device as most blogs out there claim that it's the best acclaimed advantage of the iscsi protocol other than being cheaper than the fiber channel protocol.

Any help greatly appreciated, Thanks in advance.

Zac67
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Dennisrec
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  • Iscsi (or FC for that matter) will present chunks of storage (LUNs) to your client machines. You then treat them similarly to conventional disks -- use them in LVMs (preferably), other types of volume managers or even software raid. – Brandon Xavier Nov 03 '17 at 03:51
  • And backup your data before doing anything! (my conscience is clear now) – Brandon Xavier Nov 03 '17 at 03:57
  • @Brandon Xavier, please explain better. – Dennisrec Nov 03 '17 at 04:34
  • Unless there's a further abstraction layer, a new target is an additional target and can't enlarge anything already present. Please include details to your configuration (hypervisor, targets, SAN layout) and what exactly you're trying to achieve. – Zac67 Nov 03 '17 at 06:07
  • @Zac67 yeah sure but the SAN layout is standard. Connected to tha switch and so on. Please read the question again. – Dennisrec Nov 03 '17 at 06:12
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    As Brandon has already pointed out, iSCSI targets present LUNs as block storage devices - very much like a local disk - to the initiator. That's it. An additional abstraction layer can present these, multiple disks as a single, contiguous, redundant logical disk (LVM, WSS, vSAN) - however, this is nothing dependent on iSCSI or any other SAN protocol. What is possible and how it is done depends on your specific environment you've told us nothing about. – Zac67 Nov 03 '17 at 06:20
  • @Zac67 finally. This is a well explained answer. You saved me a lot of time. – Dennisrec Nov 03 '17 at 06:27

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To provide a bit more useful answer than the comment:

iSCSI works very much as any other storage standard (Fibre Channel, SAS, SATA, ...) in that it connects a block storage (LUN on a target) to a "user" (initiator). The difference is that iSCSI uses any IP network for transport, while Fibre Channel uses a Fibre Channel network or direct cable, SAS uses a SAS cable (or expander network), SATA a SATA cable, and so on.

The initiator just reads from and writes to the storage. It doesn't care how the data is stored, it just wants to read back the exact data that's been written a while ago. The controller/target can present a single drive, a redundant array of a dozen drives, or a very large, tiered storage architecture on top of hundreds of SSDs, disks and even tape, connected by FC, SAS, anything. The initiator can even talk iSCSI to its next lower level - when it's presenting an abstraction of what's below and not even doing the storing and retrieving itself.

You could use a bunch of cheap iSCSI NASes, mount them into a storage server cluster and have them present a completely different view to the actual storage beneath via iSCSI, eg. one giant LUN. The hosts accessing the upper level have no information on what's below nor do they have to care.

So, iSCSI (or any other SAN protocol) delivers the service but the task of storage aggregation is that of the controller inside the target.

Zac67
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