Adaptec AEC-4412B Uživatelský manuál stáhnout pdf (Strana 7)

CQ-1001 / Page 7 of 14

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6,425,035

B2

7

with

menu

driven

command

interfaces.

Configuration

infor-

mation

can

be

stored

in

a

segment

of

flash

memory

and

can

be

retained

across

resets

and

power

off

cycles.

Password

protection

can

also

be

provided.

In

the

first

two

modes

of

operation,

addressing

informa-

tion

is

needed

to

map

from

FC

addressing

to

SCSI

address-

ing

and

vice

versa.

This

can

be

‘hard’

configuration

data,

due

to

the

need

for

address

information

to

be

maintained

across

initialization

and

partial

reconfigurations

of

the

Fiber

Chan-

nel

address

space.

In

an

arbitrated

loop

configuration,

user

configured

addresses

will

be

needed

for

AL_PAs

in

order

to

insure

that

known

addresses

are

provided

between

loop

reconfigurations.

With

respect

to

addressing,

FCP

and

SCSI

2

systems

employ

different

methods

of

addressing

target

devices.

Additionally,

the

inclusion

of

a

storage

router

means

that

a

method

of

translating

device

IDs

needs

to

be

implemented.

In

addition,

the

storage

router

can

respond

to

commands

without

passing

the

commands

through

to

the

opposite

interface.

This

can

be

implemented

to

allow

all

generic

FCP

and

SCSI

commands

to

pass

through

the

storage

router

to

address

attached

devices,

but

allow

for

configuration

and

diagnostics

to

be

performed

directly

on

the

storage

router

through

the

FC

and

SCSI

interfaces.

Management

commands

are

those

intended

to

be

pro-

cessed

by

the

storage

router

controller

directly.

This

may

include

diagnostic,

mode,

and

log

commands

as

well

as

other

vendor-specific

commands.

These

commands

can

be

received

and

processed

by

both

the

FCP

and

SCSI

interfaces,

but

are

not

typically

bridged

to

the

opposite

interface.

These

commands

may

also

have

side

effects

on

the

operation

of

the

storage

router,

and

cause

other

storage

router

operations

to

change

or

terminate.

Aprimary

method

of

addressing

management

commands

though

the

FCP

and

SCSI

interfaces

can

be

through

periph-

eral

device

type

addressing.

For

example,

the

storage

router

can

respond

to

all

operations

addressed

to

logical

unit

(LUN)

zero

as

a

controller

device.

Commands

that

the

storage

router

will

support

can

include

INQUIRY

as

well

as

vendor-specific

management

commands.

These

are

to

be

generally

consistent

with

SCC

standard

commands.

The

SCSI

bus

is

capable

of

establishing

bus

connections

between

targets.

These

targets

may

internally

address

logical

units.

Thus,

the

prioritized

addressing

scheme

used

by

SCSI

subsystems

can

be

represented

as

follows:

BUS:TARGET:LOGICAL

UNIT.

The

BUS

identification

is

intrinsic

in

the

configuration,

as

a

SCSI

initiator

is

attached

to

only

one-bus.

Target

addressing

is

handled

by

bus

arbi-

tration

from

information

provided

to

the

arbitrating

device.

Target

addresses

are

assigned

to

SCSI

devices

directly,

though

some

means

of

configuration,

such

as

a

hardware

jumper,

switch

setting,

or

device

specific

software

configu-

ration.

As

such,

the

SCSI

protocol

provides

only

logical

unit

addressing

within

the

Identify

message.

Bus

and

target

information

is

implied

by

the

established

connection.

Fiber

Channel

devices

within

a

fabric

are

addressed

by

a

unique

port

identifier.

This

identifier

is

assigned

to

a

port

during

certain

well-defined

states

of

the

FC

protocol.

Indi-

vidual

ports

are

allowed

to

arbitrate

for

a

known,

user

defined

address.

If

such

an

address

is

not

provided,

or

if

arbitration

for

a

particular

user

address

fails,

the

port

is

assigned

a

unique

address

by

the

FC

protocol.

This

address

is

generally

not

guaranteed

to

be

unique

between

instances.

Various

scenarios

exist

where

the

AL-PA

of

a

device

will

change,

either

after

power

cycle

or

loop

reconfiguration.

The

FC

protocol

also

provides

a

logical

unit

address

field

within

command

structures

to

provide

addressing

to

devices

10

15

20

25

30

35

40

45

50

55

60

65

8

internal

to

a

port.

The

FCP,CMD

payload

specifies

an

eight

byte

LUN

field.

Subsequent

identification

of

the

exchange

between

devices

is

provided

by

the

FQXID

(Fully

Qualified

Exchange

ID).

FC

ports

can

be

required

to

have

specific

addresses

assigned.

Although

basic

functionality

is

not

dependent

on

this,

changes

in

the

loop

configuration

could

result

in

disk

targets

changing

identifiers

with

the

potential

risk

of

data

corruption

or

loss.

This

configuration

can

be

straightforward,

and

can

consist

of

providing

the

device

a

loop-unique

ID

(AL_PA)

in

the

range

of

“01h”

to

“EFh.”

Storage

routers

could

be

shipped

with

a

default

value

with

the

assumption

that

most

configurations

will

be

using

single

storage

routers

and

no

other

devices

requesting

the

present

ID.

This

would

provide

a

minimum

amount

of

initial

con-

figuration

to

the

system

administrator.

Alternately,

storage

routers

could

be

defaulted

to

assume

any

address

so

that

configurations

requiring

multiple

storage

routers

on

a

loop

would

not

require

that

the

administrator

assign

a

unique

ID

to

the

additional

storage

routers.

Address

translation

is

needed

where

commands

are

issued

in

the

cases

FC

Initiator

to

SCSI

Target

and

SCSI

Initiator

to

FC

Target.

Target

responses

are

qualified

by

the

FQXID

and

will

retain

the

translation

acquired

at

the

beginning

of

the

exchange.

This

prevents

configuration

changes

occurring

during

the

course

of

execution

of

a

command

from

causing

data

or

state

information

to

be

inadvertently

misdirected.

Configuration

can

be

required

in

cases

of

SCSI

Initiator

to

FC

Target,

as

discovery

may

not

effectively

allow

for

FCP

targets

to

consistently

be

found.

This

is

due

to

an

FC

arbitrated

loop

supporting

addressing

of

a

larger

number

of

devices

than

a

SCSI

bus

and

the

possibility

of

FC

devices

changing

their

AL-PA

due

to

device

insertion

or

other

loop

initialization.

In

the

direct

method,

the

translation

to

BUS:TAR-

GET:LUN

of

the

SCSI

address

information

will

be

direct.

That

is,

the

values

represented

in

the

FCP

LUN

field

will

directly

map

to

the

values

in

effect

on

the

SCSI

bus.

This

provides

a

clean

translation

and

does

not

require

SCSI

bus

discovery.

It

also

allows

devices

to

be

dynamically

added

to

the

SCSI

bus

without

modifying

the

address

map.

It

may

not

allow

for

complete

discovery

by

FCP

initiator

devices,

as

gaps

between

device

addresses

may

halt

the

discovery

process.

Legacy

SCSI

device

drivers

typically

halt

discovery

on

a

target

device

at

the

first

unoccupied

LUN,

and

proceed

to

the

next

target.

This

would

lead

to

some

devices

not

being

discovered.

However,

this

allows

for

hot

plugged

devices

and

other

changes

to

the

loop

addressing.

In

the

ordered

method,

ordered

translation

requires

that

the

storage

router

perform

discovery

on

reset,

and

collapses

the

addresses

on

the

SCSI

bus

to

sequential

FCP

LUN

values.

Thus,

the

FCP

LUN

values

0-N

can

represent

N+l

SCSI

devices,

regardless

of

SCSI

address

values,

in

the

order

in

which

they

are

isolated

during

the

SCSI

discovery

process.

This

would

allow

the

FCP

initiator

discovery

pro-

cess

to

identify

all

mapped

SCSI

devices

without

further

configuration.

This

has

the

limitation

that

hot-plugged

devices

will

not

be

identified

until

the

next

reset

cycle.

In

this

case,

the

address

may

also

be

altered

as

well.

In

addition

to

addressing,

according

to

the

present

invention,

the

storage

router

provides

configuration

and

access

controls

that

cause

certain

requests

from

FC

Initiators

to

be

directed

to

assigned

virtual

local

storage

partitioned

on

SCSI

storage

devices.

For

example,

the

same

request

for

LUN

0

(local

storage)

by

two

different

FC

Initiators

can

be

directed

to

two

separate

subsets

of

storage.

The

storage

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