Simplified SCC Volume Configuration Parameter List Proposal
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
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
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
I will plan on organizing the feedback for the July Meeting in Colorado
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
= 0: SACL Assigned
MINIMUM DATA REDUNDANCY Mandatory - Provides Minimum number of Peripheral
Devices (Drives) that may fail with sustained availability.
= 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.)
Integer (0 = None Required)
PREFERRED VOLUME GROUP WIDTH Optional - Defines the Preferred Number of
Peripheral Devices To Be Used in creating the LUN.
Integer (0 = No Preferred Value Specified)
VOLUME BLOCK SIZE Optional - Defines the size of the Volume+s Block in
number of bytes.
=0: SACL Default
PREFERRED APPLICATION Optional - Enumerated Type Describing the General
IO Characteristics of the Most Important Application Using the Volume
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.
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
1: Non-Redundant - The volume is currently functional, but not protected
a drive failure.
0: Unavailable - The volume is currently unavailable due to multiple
off-line for reconfiguration.
********** VOLUME OPERATIONS **********
The minimal set of operations that are required for a Volume include the
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
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
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