SCSI Operation and Configuration

1 SCSI Operation and Configuration

SAS Implementation

The Serial Attached SCSI (SAS) interface is a point-to-point serial protocol that uses the standard SCSI command set.

The T10 technical committee of the International Committee for Information Technology Standards (INCITS) develops and maintains the SAS protocol.

The SAS protocol supports:

Serial connection
Multiple initiators
Gigabit per second data transfer rates
Scalability for media rates, distance, media, and protocols

Components

A typical SAS system consists of the following basic components:

Initiators: A device that originates requests for processing by a target.
Targets: A device (SL150 library tape drives) containing logical units and target ports that receives requests for processing and sends responses to an initiator. The target device for this document is an HP LTO-5, HP LTO-6, IBM LTO-6, IBM LTO- 7, IBM LTO-8, or IBM LTO-9 tape drive.
Expanders: Devices that provide large storage environments the ability to connect multiple targets and initiators through a switched device for scalability and redundancy. SAS benefits include improved performance, simplified cabling with the mini SAS connectors (iPass), and lower power requirements.

FC Implementation

The FC implementation on the SL150 conforms to the American National Standards Institute (ANSI) and National Committee for Information Technology Standards (NCITS), formerly X3.

The FC implementation supports:

Serial connection: Copper (electrical) or Fiber (optical) transmissions
Multiple initiators
100 MB/s data transfer rates and higher
Scalability for media rates, distance, media, and protocols

Library Support

Supports arbitrated loop and direct fabric attach
FCP (SCSI-3) command set for medium changer devices
Class 3 level of service
Private and public loop operations
Direct fabric attach operation
Hard-assigned port addresses (AL-PA)
Basic and extended link services
Connections to an external hub (or switch)
Data transfer rates of 100 MB/s
Standard approved length shortwave fibre optic cables
Multimode laser operating at 780 nm (shortwave) non-OFC

Hub Support

Multiple ports
Standard approved length fibre optic and copper cables
Multimode laser operating at 780 nm (shortwave) non-OFC
Single mode laser operating at 1300 nanometers (longwave)
Cascading hub attachments
Gigabit Interface Converter (GBIC) connections in the hub

Switch Support

Attachment to FL_Ports

Running on Both Drive Ports

When the drive has two ports, Oracle recommends that Host Application treat the second SL150 drive port as a fail over port.

The library may report a CHECK CONDITION to a command received on one port, when the other port is already busy with a library command. When a host application receives either of the following new CHECK CONDITIONs, it should reissue the command:

Not Ready, Logical Unit Offline (02/04/12h)
Aborted Command, Logical Unit Communication Failure (0Bh/08/00)
No Sense, Operation in Progress (00/00/16h)

Logical Unit Number Addressing

LUN 0 is used to communicate with the tape drive.
LUN 1 is used to communicate with the SL150 library.

Drive Element Addressing Mode Configuration

The library supports two drive element modes: addressing all drive slots or addressing the installed drives only.

The mode affects the way SCSI element addresses are reported over the library SCSI interface.

Address All Drive Slots

Setting the mode to Address All Drive Slots results in the following:

All drive slots (empty or installed) are reported to the host application over the library SCSI interface. Using this mode allows for the addition of new tape drives without restarting the library.
Each drive and empty drive bay is assigned a drive SCSI Element Address. Drive element addresses are assigned sequentially starting at 500 for each partition from the topmost drive in the partition to the bottom drive in the partition. Similarly, for non-partitioned libraries, drive element address are also assigned sequentially starting at 500 from the top of the library to the bottom of the library.
A SCSI MODE SENSE command requesting the Element Address Assignment page will end in Good status. The total number of data transfer elements reported will include empty drive bays.
A SCSI READ ELEMENT STATUS command that includes an empty drive slot will end in Good status. The Data Transfer Element Descriptor data for the empty drive slot will return the ED bit set to 1 (disabled) and an exception condition indicating an Empty Drive Bay; the Except Bit will be set to 1, the ASC field will be set to 3Bh, and the ASCQ field will be set to 1Ah.
A SCSI MOVE command from an empty drive slot will end in Check Condition Status. The sense data will indicate Illegal Request, Source Empty (Sense Key = 5h, ASC = 3Bh, ASCQ = 0Eh).
A SCSI MOVE command to an empty drive slot will end in Check Condition Status. The sense data will indicate Illegal Request, Empty Drive Bay (Sense Key = 5h, ASC = 3Bh, ASCQ = 1Ah).
A SCSI POSITION TO ELEMENT command to an empty drive slot will end in Good Status. The robot will move in front of the empty drive bay.

Address Installed Drives Only

Setting the mode to Address Installed Drives Only results in the following:

Only drives present at initialization are reported to a host application over the library SCSI interface. If a new drive is added, the library must be rebooted before the new drive can be used by a host application.
Each installed drive is assigned a drive SCSI Element Address during library initialization. Drive element addresses are assigned sequentially starting at 500 for each partition from the topmost drive in the partition to the bottom drive in the partition. Similarly, for non-partitioned libraries, drive element address are also assigned sequentially starting at 500 from the top of the library to the bottom of the library.
A SCSI MODE SENSE command requesting the Element Address Assignment page will end in Good status. The total number of data transfer elements reported will include only the number of drives found to be present at initialization.
If a drive is removed, a SCSI READ ELEMENT STATUS command for the now empty drive slot will end in Good status. The Data Transfer Element Descriptor data for the empty drive slot will return the ED bit set to 1 (disabled) and an exception condition indicating a Tape Drive error; the Except Bit will be set to 1, the ASC field will be set to 40h, and the ASCQ field will be set to 02h.

Multiple Initiator Support

The library supports unit reserve, release, and persistent reserve commands. Host software should reserve resources whenever possible.
The library does not maintain a separate "prevent" or "allow" state for each initiator. There is a single state for all initiators. Therefore, if any initiator sends a Prevent Medium Removal command, the library locks the CAPs. If any initiator sends an Allow Media Removal command, the library unlocks the CAPs. For more information, see Prevent/Allow Medium Removal (1Eh).

Host Timeout Characteristics

Host timeout values for SCSI commands may require adjustment based on the configuration of the library.

Reservation Handling

The library supports the following reservation management methods:

Reserve and Release — defined by the ANSI SCSI-3 Primary Commands (SPC-2) Standard. See Table 1-1 for command reservation restrictions.
Persistent Reservation — defined by the ANSI SCSI-3 Primary Commands (SPC-3) Standard. See Table 1-2 for command reservation restrictions.

Table 1-1 and Table 1-2 use the following definitions:

Conflict — The library terminates the command with a Reservation Conflict (18h) status.
Allowed — The library executes the command normally.

Compatible Reservation Handling Bit

The library returns 0 for the Compatible Reservation Handling (CRH) bit in the Persistent Reserve In (5Eh) Report Capabilities Data page.

A CRH value of 0 indicates the library processed the reserve or release command as defined in SPC-2. Therefore, the library will return a Reservation Conflict (18h) when it receives a reserve or release command from the same initiator that holds the persistent reservation.

Reserve and Release Management Method Command Restrictions

Table 1-1 Action when the Library is Reserved by Another Initiator

Command	HP Bridged Drive	IBM Bridged Drive
Initialize Element Status (07h)	Conflict	Conflict
Initialize Element Status w/Range (37h)	Conflict	Conflict
Inquiry (12h)	Allowed	Allowed
Log Sense (4Dh)	Allowed	Allowed
Mode Select (15h/55h)	Conflict	Conflict
Mode Sense (1Ah/5Ah)	Conflict	Allowed
Move Medium (A5h)	Conflict	Conflict
Persistent Reserve In (5Eh)	Conflict	Conflict
Persistent Reserve Out (5Fh)	Conflict	Conflict
Position to Element (2Bh)	Conflict	Conflict
Prevent/Allow Media Removal (1Eh)	Prevent = 0, Allowed Prevent = 1, Conflict	Prevent = 0, Allowed Prevent = 1, Conflict
Read Element Status (B8h)	Conflict	Conflict
Release (17h)	Allowed^Foot 1	Allowed^Foot 2
Report LUNs (A0h)	Allowed	Allowed
Report Target Port Groups (A3h)	Allowed	Allowed
Request Sense (03h)	Allowed	N/A^Foot 3
Request Volume Element Address (B5h)	Conflict	Allowed
Reserve (16h)	Conflict	Conflict
Send Diagnostics (1Dh)	Conflict	Conflict
Send Volume Tag (B6h)	Conflict	Conflict
Test Unit Ready (00h)	Conflict	Conflict

^Footnote 1

The reservation is not released.

^Footnote 2

The reservation is not released.

^Footnote 3

The Report Target Port Group command is not supported by the IBM drive.

Persistent Reservation Management Method Command Restrictions

Table 1-2 Persistent Reservation Command Restrictions when the Library is Reserved by Another Initiator

Command	Non-Registered Initiator	Registered Initiator: Exclusive Access Reservation	Registered Initiator: Exclusive Access Registrant Only
Initialize Element Status (07h)	Conflict	Conflict	Allowed
Initialize Element Status w/Range (37h)	Conflict	Conflict	Allowed
Inquiry (12h)	Allowed	Allowed	Allowed
Log Sense (4Dh)	Allowed	Allowed	Allowed
Mode Select (15h/55h)	Conflict	Conflict	Allowed
Mode Sense (1Ah/5Ah) HP Drive	Conflict	Conflict	Allowed
Mode Sense (1Ah/5Ah) IBM Drive	Allowed	Allowed	Allowed
Move Medium (A5h)	Conflict	Conflict	Allowed
Persistent Reserve In (5Eh)	Allowed	Allowed	Allowed
Persistent Reserve Out (5Fh) - SA=Register	Allowed	Allowed	Allowed
Persistent Reserve Out (5Fh) - SA=Reserve	Conflict	Conflict	Conflict
Persistent Reserve Out (5Fh) - SA=Release	Conflict	Allowed^Foot 4	Allowed^Foot 5
Persistent Reserve Out (5Fh) - SA=Clear	Conflict	Allowed	Allowed
Persistent Reserve Out (5Fh) - SA=Preempt	Conflict	Allowed	Allowed
Persistent Reserve Out (5Fh) - SA=Preempt/Abort	Conflict	Allowed	Allowed
Persistent Reserve Out (5Fh) - SA=Register and Ignore	Allowed	Allowed	Allowed
Persistent Reserve Out (5fh) - SA=Resister and Move	Conflict	Conflict	Conflict
Position to Element (2Bh)	Conflict	Conflict	Allowed
Prevent/Allow Media Removal (1Eh) Prevent = 0	Allowed	Allowed	Allowed
Prevent/Allow Media Removal (1Eh) Prevent = 1	Conflict	Conflict	Allowed
Read Element Status (B8h) HP Drive	Conflict	Conflict	Allowed
Read Element Status (B8h) IBM Drive	Allowed	Allowed	Allowed
Release (17h)	Conflict	Conflict	Allowed
Report LUNs (A0h)	Allowed	Allowed	Allowed
Report Target Port Groups (A3h)^Foot 6	Allowed	Allowed	Allowed
Request Sense (03h)	Allowed	Allowed	Allowed
Request Volume Element Address (B5h)	Conflict	Conflict	Allowed
Reserve (16h)	Conflict	Conflict	Allowed
Send Diagnostics (1Dh)	Conflict	Conflict	Allowed
Send Volume Tag (B6h)	Conflict	Conflict	Allowed
Test Unit Ready (00h) HP Drive	Allowed	Allowed	Allowed
Test Unit Ready (00h) IBM Drive	Conflict	Conflict	Allowed

^Footnote 4

The reservation is not released.

^Footnote 5

The reservation is not released.

^Footnote 6

HP Drive Only. The Report Target Port Group command is not supported by the IBM drive

SCSI Element Addressing

Element addressing starts at a certain value for each component type.

Table 1-3 Starting Element Address and Maximum Number of Elements

Element Type	First Element Address	Maximum Number of Elements for an SL150 Library with 15 Modules and the Standard Mailslot Configuration	Maximum Number of Elements for an SL150 Library with 15 Modules and the Expanded Mailslot Configuration
Hand	0	1	1
Mailslot	10	4	19
Drives	500	30	30
Storage Slots	1000	450	435

Behavior During LTO9 Tape Calibration

When LTO9 media is first loaded into the LTO9 drive, the drive automatically initiates tape calibration, which includes initialization and characterization of the cartridge. IBM has stated that LTO9 calibration may require 20 minutes to 2 hours to complete.

In order to accommodate host time out constraints during calibration, special processing is added:

The SCSI interface returns GOOD status to the host as soon as the library determines that the IBM LTO9 drive is calibrating the tape.
- Normally, when fast mode is disabled, the library waits until the tape drive indicates the tape is loaded and the drive is ready to accept SCSI commands on the data path.
- During calibration, the drive interface returns Not Ready, Becoming Ready to SCSI commands on the data path: Sense Key = 02, ASC = 04h, ASCQ = 01h.
If the host issues a dismount command while the drive is calibrating, the library returns a Check Condition, Illegal Request, Medium Not Present, Drive Not Unloaded: Sense Key = 05h, ASC = 3Ah, ASCQ = 00h.