RE: iSCSI virtualization proposal

["Douglas Otis" <dotis@sanlight.net>]

Don,

This goes to the issue of bootstrapping.  The discovery process should be
extraction of information from an LDAP server.

Doug

>
> How would discovery work in this scenario?
> (What would who "find"?)
>
> Don Deel
> don@prisa.com
>
>
> -----Original Message-----
> Date: Thu, 12 Oct 2000 11:54:12 +0200
> From: Yaron Klein <klein@eng.tau.ac.il>
> Organization: Tel-Aviv University
> To: ips@ece.cmu.edu
> Subject: iSCSI virtualization proposal
>
> Proposal for iSCSI virtualization:
>
> The problem:
>
> In order to implement iSCSI virtualization in a local network, we
> need the following topology:
>
>   -----------
>   |         |
>   | host    |
>   |         |
>   -----------
>        |
>        |
>        |
> ---------------------------------------------------------
>      |              |                |              |
>      |              |                |              |
>      |              |                |              |
> ----------      ----------      ----------      ----------
> |        |      |        |      |        |      |        |
> | Manager|      | Disk A |      | Disk B |      | Disk C |
> |        |      |        |      |        |      |        |
> ----------      ----------      ----------      ----------
>
> When the host is an iSCSI initiator, the disks are iSCSI targets
> and the manager is with iSCSI target port to the host and iSCSI
> initiator port to the disks.
>
> The host considers the manager as a “flat” disk space with iSCSI
> port and is unaware of the disks. The manager manages the disks
> in some algorithm to construct a combined virtual volume.
>
> Consider the following example:
>
> Each disk contains 1000 blocks. The virtual volume is thus 3000
> blocks. The hosts sends an iSCSI command to the manager to read
> 40 blocks from address 500. The physical addresses are: A –
> 400:409, B – 300:319 and C – 600:609.
>
> In the current iSCSI protocol, the traffic scenario is:
>
> Host -> manager: iSCSI command, read from 500 size 40.
> Manager -> A: iSCSI command, read from 400 size 10.
> A -> manager: iSCSI data.
> A -> manager: iSCSI status.
> Manager -> host: iSCSI data.
> Manager -> B: iSCSI command, read from 300 size 20.
> B -> manager: iSCSI data.
> B -> manager: iSCSI status.
> Manager -> host: iSCSI data.
> Manager -> C: iSCSI command, read from 600 size 10.
> C -> manager: iSCSI data.
> C -> manager: iSCSI status.
> Manager -> host: iSCSI data.
> Manager -> host: iSCSI status.
>
> Problem 1: Traffic on the line is double! Each data packet is
> transferred twice (from disk to manager and from manager to host).
>
> Problem 2: The manager is a bottleneck. Both data and commands of
> all the system (assuming many hosts and disks) is transferred via it.
>
> Solution:
>
> Lets add in the iSCSI status message, in the “iSCSI status”
> field, the following option:
>
> 2 - iSCSI reflection
>
> Which means that the status contains add-ons of iSCSI command
> that the host should implement. These commands will implement the
> original request. In our example it will look as:
>
> Host -> manager: iSCSI command, read from 500 size 40.
> Manager -> host: iSCSI status (with reflection), iSCSI commands
> (for A, B and C)
> host -> A: iSCSI command, read from 400 size 10.
> A -> host: iSCSI data.
> A -> host: iSCSI status.
> host -> B: iSCSI command, read from 300 size 20.
> B -> host: iSCSI data.
> B -> host: iSCSI status.
> host -> C: iSCSI command, read from 600 size 10.
> C -> host: iSCSI data.
> C -> host: iSCSI status.
>
> Benefits:
>
> * Data traffic on the line is single.
> * No bottleneck on the manager.
>
> Note: The manager is a software pack. It can be an independent
> unit, in the host or in one of the disk. It is just schematically
> stated as independent unit.
>
> In conclusion, the addition of the reflection feature in the
> protocol is minor change, can be optional and will enable the
> enormous potential of virtualization.
>
> Comments are more than welcome,
>
> Yaron Klein
> SANRAD
>
> klein@sanrad.com
>