Simplified SCC Volume Configuration Parameter List Proposal

DeKoning, Rod rdekonin at ppdpost.ks.symbios.com
Thu May 23 13:23:00 PDT 1996


* From the SCSI Reflector, posted by:
* "DeKoning, Rod" <rdekonin at ppdpost.ks.symbios.com>
*

     Date:Document Created: 05/16/96 3:41 PM   Last Updated: 05/23/96 2:14 
PM

     To:  X3T10 Chairman, Members of X3T10 SCC Working Group
          
     From:     Rod DeKoning, Symbios Logic
          
     Subject:  Simplified SCC Command Set

During the May SCC joint meeting of the RAB and X3T10 SCSI group, a 
suggestion was made that a simplified RAID Configuration command set be 
provided as part of SCC that would allow those users of RAID to specify a 
Volume without specifying the gory details of the RAID mapping.  Such a 
mapping is desirable because of the following characteristics of SCC:

1. SCC currently requires the specification of the RAID mapping by the 
interface to the
SCC device.  This often requires the utility designer (and normally user) to 
make  decisions that they are not necessarily prepared/qualified to make. 
 In many cases, the
SCC device software is more informed to make these decisions.

2. SCC does not provide a mechanism to easily understand what parameters or
combinations of parameters are supported when configuring a Volume.

3. SCC does not provide a mechanism to provide mappings for newer RAID 
mappings
that are dynamic in nature.

The first step in putting together such a command(s) is to agree upon a set 
of parameters that would allow this simplified interface.   The following 
describes a first cut at such a list.  Please provide feedback as to the 
MINIMUM set of parameters that would be required in a Simplified +Create 
Volume+ command.

I will plan on organizing the feedback for the July Meeting in Colorado 
Springs.

Note: Not included in this interface is Enclosure Management - the currently 
proposed SCSI Enclosure Services interface and the existing SCC1 interface 
cover this adequately.


**********          CONFIGURING A VOLUME          **********
The following pieces of information are necessary or useful to the admin. 
when configuring a User Volume:

VOLUME SIZE    Mandatory - Provides requested user capacity in # of blocks

     
VOLUME LUN IDENTIFIER    Optional - Provides the Initial V-LUI assignment
Values:
     = 0: SACL Assigned

MINIMUM DATA REDUNDANCY Mandatory - Provides Minimum number of Peripheral
Devices (Drives) that may fail with sustained availability.
Values:
= 0:  No Redundancy - No Redundancy 

     - e.g. RAID 0
= 1:  Sentinel Redundancy - Minimum of Single Drive Redundancy within Group
     - e.g. RAID 5, RAID 3
= 2 - 127:  - Platoon Redundancy - >1 Drive Redundancy within Group 

     - e.g. RAID 6 or with spared media protection
= 128: Mirrored Redundancy - All data maintained with separate copy 

     - e.g. RAID 1
= 129-255: Mirrored Redundancy with spared media protection

MINIMUM PERIPHERAL CHANNEL FAILURE TOLERANCE Mandatory - Provides Minimum 
Acceptable Number of Channel Failures that must be tolerated.  (i.e. This 
parameter would specify whether a peripheral device channel failure would be 

allowed to make user data unavailable.)
Values:   
Integer (0 = None Required)


PREFERRED VOLUME GROUP WIDTH  Optional - Defines the Preferred Number of
Peripheral Devices To Be Used in creating the LUN.
Values:   
Integer (0 = No Preferred Value Specified)


VOLUME BLOCK SIZE   Optional - Defines the size of the Volume+s Block in
number of bytes.
Values:   
=0: SACL Default


PREFERRED APPLICATION    Optional - Enumerated Type Describing the General 
IO Characteristics of the Most Important Application Using the Volume
Values:   
0 - No Preference
1 - Through Put Centric Application, e.g. OLTP Applications
2 - High Bandwidth Applications, e.g. Multi-Media Applications



**********          VOLUME STATUS REPORTING       **********
The following parameters would be reported in addition to the values that 
would be set as described above:

VOLUME STATUS  Mandatory - Provides the number of device failures that
will make the volume unavailable.
Values:   
3-127: Multi-Sentinel Redundant - The volume is currently protected against
(Volume Status - 2)  device failures.
2: Sentinel Redundant - The volume is currently protected against a single 
device
failure.
1: Non-Redundant - The volume is currently functional, but not protected 
against
a drive failure.
0: Unavailable - The volume is currently unavailable due to multiple 
failures or
off-line for reconfiguration.



**********          VOLUME OPERATIONS        **********
The minimal set of operations that are required for a Volume include the 
following:

ADD VOLUME SET Mandatory - Provides the mechanism for creating a Volume
using the above parameters.

DELETE VOLUME SET   Use DELETE VOLUME SET service action of SCC 1

MODIFY VOLUME SET   Optional - Provides the mechanism for modifying 
parameters of a  Volume (restricted to the above parameters) without 
destroying user data.

VERIFY VOLUME SET   Use VERIFY VOLUME SET CHECK DATA service action of SCC 
1.

CORRECT PARITY OF VOLUME      Use RECALCULATE VOLUME SET CHECK DATA
service action of SCC 1.

Note: It is expected that these operations would be part of an action field 
or command structure in the new configuration volume command.


**********          PERIPHERAL DEVICE  OPERATIONS      **********
Leave this to current SCC1 Interface


**********          SPARE ASSIGNMENTS        **********
Leave this to current SCC1 interface.


**********          REDUNDANCY MAPPING       **********
Leave this to the vendor.


**********          COMPONENT MONITORING          **********
Leave this to the SCSI Enclosure Services Command Set being developed by Bob 
Snively, et.al.










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