Appendix d. enabling lun support in linux, Appendix, Enabling – Dell TL2000 User Manual

Page 239: Support, Linux

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Appendix

D.

Enabling

LUN

Support

in

Linux

To

verify

the

detection

of

a

tape

drive,

administrators

should

check

for

its

entry

in

/proc/scsi/scsi

.

Current

versions

of

Linux

may

not

scan

the

logical

storage

unit

(LUN)

ID

of

every

device.

This

can

result

in

some

PowerVault

devices

not

being

identified

or

listed

in

the

/proc/scsi/scsi

output.

Administrators

can

follow

these

steps

to

enable

support

for

such

devices.

1.

Type

cat/proc/scsi/scsi

.

The

output

will

look

similar

to

the

following:

Attached

devices:

Host:

scsi3

Channel:

00

Id:

00

Lun:

00

Vendor:

IBM

Model:

ULTRIUM-TD3

Rev:

5BG2

Type:

Sequential-Access

ANSI

SCSI

revision:

03

2.

Identify

the

host

adapter,

channel

number,

target

ID

number,

and

LUN

number

for

the

first

LUN

of

the

device

to

be

configured.

In

this

example,

the

Certance

Ultrium

2

(a

drive

in

the

PowerVault

124T)

is

shown

at

the

address,

or

nexus,

3

0

0

0

—

which

means

host

adapter

3,

channel

number

0,

ID

0,

and

LUN

0.

The

PowerVault

124T

always

has

the

tape

drive

at

LUN

0

and

the

robot

at

LUN

1.

3.

For

each

LUN

that

needs

to

be

discovered

by

Linux,

issue

the

following

command:

echo

"scsi-add-single-device

H

C

I

L">/proc/scsi/scsi

H

C

I

L

refers

to

the

nexus

described

in

step

2.

So,

with

the

PowerVault

124T

robot

configured

at

LUN

1,

type:

echo

"scsi-add-single-device

3

0

0

1">/proc/scsi/scsi

.

The

echo

command

will

force

a

scan

of

each

device

at

the

given

nexus.

4.

Type

cat

/proc/scsi/scsi

again

to

verify

that

all

devices

are

now

listed.

The

output

will

look

similar

to

the

following:

Attached

devices:

Host:

scsi3

Channel:

00

Id:

00

Lun:

00

Vendor:

IBM

Model:

ULTRIUM-TD3

Rev:

5BG2

Type:

Sequential-Access

ANSI

SCSI

revision:

03

Attached

devices:

Host:

scsi3

Channel:

00

Id:

00

Lun:

01

Vendor:

DELL

Model:

PV-124T

Rev:

V31

Type:

Sequential-Access

ANSI

SCSI

revision:

03

Administrators

should

add

the

echo

command

to

the

Linux

boot

scripts

because

the

device

information

is

not

persistent

and

must

be

created

each

time

the

system

boots

up.

One

example

file

that

can

be

used

for

storing

the

commands

is

/etc/rc.local.

Note

that

configuring

additional

devices

on

a

server

or

a

storage

area

network

(SAN)

can

cause

the

devices

to

be

reordered,

which

requires

administrators

to

modify

the

commands.

If

the

Fibre

Channel

adapter

supports

Persistent

Bindings

or

an

equivalent

function,

it

can

be

enabled

to

reduce

the

chance

of

devices

being

reordered

upon

discovery.

Note:

This

procedure

must

be

run

each

time

the

server

is

booted.

Also,

if

backup

application

services

are

running

(for

example,

they

automatically

start

when

the

OS

loads),

they

must

be

disabled

and

re-enabled

after

the

above

procedure.

The

other

way

to

enable

LUN

support

is

to

recompile

the

kernel

and

enable

LUN

scanning

in

the

Adaptec

driver,

but

it

requires

advanced

knowledge

of

Linux

and

will

not

be

covered

here.

However,

it

will

allow

the

server

to

always

boot

and

see

the

device

without

any

manual

procedures.

D-1