配置LIO iSCSI Target

現在主流Linux都可以設定iSCSI，如STGT/TGT、LIO Target等。Linux-IO（LIO）Target是目前Linux标準的iSCSI target的開源實作，包含在Linux核心（2.6.38後）中。LIO不發起會話，而是提供LUNs，等待來自SCSI initiator的指令并進行所需的I/O資料傳輸。更詳細的參考：http://en.wikipedia.org/wiki/LIO_Target

設定一個target，包含以下元件：

儲存設備：使用Linux作為target，可以使用LVM邏輯卷來作為底層儲存設備，也可以使用其他儲存設備，如分區、硬碟、稀疏檔案等。

LUN ID：每個通過iSCSI target共享的儲存設備是當做一個LUN來共享，每個LUN都有一個唯一ID。

Target ID：如果想要授權target連接配接到特定節點，建立不同的target，每個target有自己的target ID，也稱為IQN（Internet Qualifiied Name）。iSCSI用戶端使用IQN來進行連接配接。

Identifier：辨別符用來識别特定的iSCSI target。

端口号：target監聽的TCP端口，預設是3260。

CentOS7上使用targetcli指令來設定iSCSI target.

# systemctl enable target.service

# systemctl start target.service

targetcli支援不同的後端存儲，當建立iSCSI磁盤時，必須指定後端存儲類型。targetcli來檢視可用的後端存儲。

# targetcli
targetcli shell version 2.1.fb34
Copyright 2011-2013 by Datera, Inc and others.
For help on commands, type 'help'.

/> ls
o- / ............................................................................... [...]
  o- backstores .................................................................... [...]
  | o- block ........................................................ [Storage Objects: 0]
  | o- fileio ....................................................... [Storage Objects: 0]
  | o- pscsi ........................................................ [Storage Objects: 0]
  | o- ramdisk ...................................................... [Storage Objects: 0]
  o- iscsi .................................................................. [Targets: 0]
  o- loopback ............................................................... [Targets: 0]

添加LVM，使用指令“/backstores/fileio create lun1 /opt/disk1.img 100M”可以添加一個稀疏檔案的target。

/> /backstores/block create lun0 /dev/rootvg/image 
Created block storage object lun0 using /dev/rootvg/image.
/> ls
o- / ............................................................................... [...]
  o- backstores .................................................................... [...]
  | o- block ........................................................ [Storage Objects: 1]
  | | o- lun0 ........................ [/dev/rootvg/image (5.0GiB) write-thru deactivated]
  | o- fileio ....................................................... [Storage Objects: 0]
  | o- pscsi ........................................................ [Storage Objects: 0]
  | o- ramdisk ...................................................... [Storage Objects: 0]
  o- iscsi .................................................................. [Targets: 0]
  o- loopback ............................................................... [Targets: 0]

定義target

/> /iscsi create
Created target iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625.
Created TPG 1.

檢視建立的TPG

/> ls
o- / ............................................................................... [...]
  o- backstores .................................................................... [...]
  | o- block ........................................................ [Storage Objects: 1]
  | | o- lun0 ........................ [/dev/rootvg/image (5.0GiB) write-thru deactivated]
  | o- fileio ....................................................... [Storage Objects: 0]
  | o- pscsi ........................................................ [Storage Objects: 0]
  | o- ramdisk ...................................................... [Storage Objects: 0]
  o- iscsi .................................................................. [Targets: 1]
  | o- iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625 ............ [TPGs: 1]
  |   o- tpg1 ..................................................... [no-gen-acls, no-auth]
  |     o- acls ................................................................ [ACLs: 0]
  |     o- luns ................................................................ [LUNs: 0]
  |     o- portals .......................................................... [Portals: 0]
  o- loopback ............................................................... [Targets: 0]

使用預設配置建立portal

/> cd /iscsi/iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625/tpg1/
/iscsi/iqn.20...60959625/tpg1> portals/ create
Using default IP port 3260
Binding to INADDR_ANY (0.0.0.0)
Created network portal 0.0.0.0:3260.
/iscsi/iqn.20...60959625/tpg1>

指定LUN到portal，如果想要對LUN進行通路限制，使用iSCSI initiator的IQN，然後檢視目前設定，最終saveconfig儲存。

Created network portal 0.0.0.0:3260.
/iscsi/iqn.20...60959625/tpg1> luns/ create /backstores/block/lun0
Created LUN 0.
/iscsi/iqn.20...60959625/tpg1> acls/ create iqn.2014-03.com.example:123456789
Created Node ACL for iqn.2014-03.com.example:123456789
Created mapped LUN 0.
/iscsi/iqn.20...60959625/tpg1> ls
o- tpg1 ........................................................... [no-gen-acls, no-auth]
  o- acls ...................................................................... [ACLs: 1]
  | o- iqn.2014-03.com.example:123456789 ................................ [Mapped LUNs: 1]
  |   o- mapped_lun0 .............................................. [lun0 block/lun0 (rw)]
  o- luns ...................................................................... [LUNs: 1]
  | o- lun0 ............................................. [block/lun0 (/dev/rootvg/image)]
  o- portals ................................................................ [Portals: 1]
    o- 0.0.0.0:3260 ................................................................. [OK]
/iscsi/iqn.20...60959625/tpg1> cd /
/> ls
o- / ............................................................................... [...]
  o- backstores .................................................................... [...]
  | o- block ........................................................ [Storage Objects: 1]
  | | o- lun0 .......................... [/dev/rootvg/image (5.0GiB) write-thru activated]
  | o- fileio ....................................................... [Storage Objects: 0]
  | o- pscsi ........................................................ [Storage Objects: 0]
  | o- ramdisk ...................................................... [Storage Objects: 0]
  o- iscsi .................................................................. [Targets: 1]
  | o- iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625 ............ [TPGs: 1]
  |   o- tpg1 ..................................................... [no-gen-acls, no-auth]
  |     o- acls ................................................................ [ACLs: 1]
  |     | o- iqn.2014-03.com.example:123456789 .......................... [Mapped LUNs: 1]
  |     |   o- mapped_lun0 ........................................ [lun0 block/lun0 (rw)]
  |     o- luns ................................................................ [LUNs: 1]
  |     | o- lun0 ....................................... [block/lun0 (/dev/rootvg/image)]
  |     o- portals .......................................................... [Portals: 1]
  |       o- 0.0.0.0:3260 ........................................................... [OK]
  o- loopback ............................................................... [Targets: 0]
/> saveconfig 
Last 10 configs saved in /etc/target/backup.
Configuration saved to /etc/target/saveconfig.json

連接配接到iSCSI SAN

使用iscsiadm指令來連接配接到iSCSI target。iscsiadm有不同模式，每一個模式來處理iSCSI連接配接的不同階段。

• discoverydb/discovery: 用來查詢iSCSI target并找出可用target。

• node:登入到特定的iSCSI target。

• session: 從目前會話擷取資訊或者建立一個新的會話到已經連接配接的target。

• iface和host: 允許指定連接配接到特定target的方式。

當連接配接到iSCSI target後，會自動建立配置檔案，機器重新開機後，伺服器會自動連接配接到以前的iSCSI連接配接。在用iscsiadm連接配接iSCSI target前，需要確定相關module已經加載。

第一步：Discovery模式

使用iscsiadm --mode discovery --type sendtargets --portal xxxx:3260 --discover來發現iSCSI target。

# iscsiadm --mode discovery --type sendtargets --portal 10.0.0.11:3260 --discover
10.0.0.11:3260,1 iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625

上面的指令不僅顯示target的名字，并且将iSCSI配置添加到/var/lib/iscsi/send_targets目錄下（redhat）。可以使用“-P”（0或1代表debug級别）選項來輸出儲存的資訊。從下面可以看出是使用SENDTARGETS發現類型。

# iscsiadm --mode discoverydb -P 1
SENDTARGETS:
DiscoveryAddress: 10.0.0.11,3260
Target: iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625
        Portal: 10.0.0.11:3260,1
                Iface Name: default
iSNS:
No targets found.
STATIC:
No targets found.
FIRMWARE:
No targets found.

根據不同的SAN環境，所有的發現類型都可用，iSNS可以設定一個iSNS伺服器，它集中注冊了iSCSI target。fireware是使用iSCSI硬體擴充卡可以發現iSCSI target。SLP目前不可用。

第二步：node模式

在執行上一步後，可以知道taget的IQN。下一步登入target來建立連接配接。node模式是iSCSI術語，表示iSCSI target和特定的portal之間的實際連接配接。portal是連接配接到iSCSI target的位址和端口。

# iscsiadm --mode node --targetname iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625 --portal 10.0.0.11:3260 --login             
Logging in to [iface: default, target: iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625, portal: 10.0.0.11,3260] (multiple)
Login to [iface: default, target: iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625, portal: 10.0.0.11,3260] successful.

使用lsscsi指令可以驗證連接配接，發現新增了LIO-ORG類型的/dev/sdb。

# lsscsi
[1:0:0:0]    cd/dvd  NECVMWar VMware IDE CDR10 1.00  /dev/sr0 
[2:0:0:0]    disk    VMware,  VMware Virtual S 1.0   /dev/sda 
<span style="color:#ff6600;">[3:0:0:0]    disk    LIO-ORG  lun0             4.0   /dev/sdb </span>

在建立連接配接後，iSCSI initiator會将配置寫到$ISCSI_ROOT/nodes目錄。default檔案包含了連接配接到iSCSI target的設定。

# ls -lR
.:
total 0
drw-------. 3 root root 29 Nov  7 03:41 iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625

./iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625:
total 0
drw-------. 2 root root 20 Nov  7 03:41 10.0.0.11,3260,1

./iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625/10.0.0.11,3260,1:
total 4
-rw-------. 1 root root 2064 Nov  7 03:41 default

第三步：管理iSCSI連接配接

檢視目前連接配接資訊：

# iscsiadm --mode node -P 1  
Target: iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625
        Portal: 10.0.0.11:3260,1
                Iface Name: default

擷取更詳細的資訊：

# iscsiadm --mode session -P 2
Target: iqn.2003-01.org.linux-iscsi.controller.x8664:sn.bb2460959625 (non-flash)
        Current Portal: 10.0.0.11:3260,1
        Persistent Portal: 10.0.0.11:3260,1
                **********
                Interface:
                **********
                Iface Name: default
                Iface Transport: tcp
                Iface Initiatorname: iqn.1994-05.com.redhat:c4e61affa28
                Iface IPaddress: 10.0.0.31
                Iface HWaddress: <empty>
                Iface Netdev: <empty>
                SID: 1
                iSCSI Connection State: LOGGED IN
                iSCSI Session State: LOGGED_IN
                Internal iscsid Session State: NO CHANGE
                *********
                Timeouts:
                *********
                Recovery Timeout: 120
                Target Reset Timeout: 30
                LUN Reset Timeout: 30
                Abort Timeout: 15
                *****
                CHAP:
                *****
                username: <empty>
                password: ********
                username_in: <empty>
                password_in: ********
                ************************
                Negotiated iSCSI params:
                ************************
                HeaderDigest: None
                DataDigest: None
                MaxRecvDataSegmentLength: 262144
                MaxXmitDataSegmentLength: 262144
                FirstBurstLength: 65536
                MaxBurstLength: 262144
                ImmediateData: Yes
                InitialR2T: Yes
                MaxOutstandingR2T: 1

使用iscsi存儲

在成功建立連接配接後，通過fdisk -l可以發現新磁盤，可以當普通的本地磁盤使用。

# fdisk -l

Disk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000b68ef

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    41943039    20458496   8e  Linux LVM

Disk /dev/mapper/centos_compute-swap: 2147 MB, 2147483648 bytes, 4194304 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk /dev/mapper/centos_compute-root: 18.8 GB, 18798870528 bytes, 36716544 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

<span style="color:#ff6600;">Disk /dev/sdb: 5368 MB, 5368709120 bytes, 10485760 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 4194304 bytes</span>

斷開連接配接會話

iSCSI預設設定在重新開機後伺服器後自動重連。如果需要斷開連接配接，必須移走配置。通過iscsiadm --mode node --logout來斷開會話，這個指令會斷開所有連接配接，同時删除對應配置。

LIO iSCSI配置及使用配置LIO iSCSI Target

配置LIO iSCSI Target

連接配接到iSCSI SAN

使用iscsi存儲

斷開連接配接會話

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