Linux 下的 iSCSI initiator 部署 =============================== .. versionadded:: @2014-04-11 创建 以 Ubuntu 系统上部署 :wiki:`iSCSI` initiator 为例,首先执行 `apt-get install open-iscsi multipath-tools` 安装必要的软件。前者为 iSCSI initiator 软件,后者提供 :wiki:`multipath ` 支持。 iSCSI initiator 的部署过程非常简单,依次如下操作即可: #. 发现 target :: # iscsiadm -m discovery -t sendtargets -p 192.168.2.200:3260 192.168.2.201:3260,0 iqn.1997-05.xxxxxx:default-target 192.168.2.200:3260,0 iqn.1997-05.xxxxxx:default-target 这里可以看到该 target 有两个 ip 地址,可以配置 multipath 支持。 #. 依次登录上一步输出的 target 和 ip 地址,并设置自动登录: :: # iscsiadm -m node --targetname iqn.1997-05.xxxxxx:default-target -p 192.168.2.201 --login Logging in to [iface: default, target: iqn.1997-05.xxxxxx:default-target, portal: 192.168.2.201,3260] Login to [iface: default, target: iqn.1997-05.xxxxxx:default-target, portal: 192.168.2.201,3260]: successful # iscsiadm -m node --targetname iqn.1997-05.xxxxxx:default-target --op update -n node.startup -v automatic 此时 dmesg 能看到内核的输出信息如下: :: scsi1 : iSCSI Initiator over TCP/IP scsi 1:0:0:0: Direct-Access Proware proIPS 120 PQ: 0 ANSI: 4 sd 1:0:0:0: [sdb] 2306867200 512-byte logical blocks: (1.18 TB/1.07 TiB) sd 1:0:0:0: [sdb] Write Protect is off sd 2:0:0:0: [sdb] Mode Sense: bb 00 00 00 sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA sdb: sdb1 sd 1:0:0:0: [sdb] Attached SCSI disk 如果在发现 target 时没有多个 ip,则 iSCSI 的配置到此结束。后续可以直接对 sdb 进行相关操作即可。 #. 多路径支持 如果有多个 ip,则可以继续配置多路径的支持。 :: # multipath -ll 32017001378a8a9ff dm-0 Proware,proIPS size=1.1T features='0' hwhandler='0' wp=rw \`-+- policy='round-robin 0' prio=1 status=active |- 1:0:0:0 sdb 8:16 active ready running \`- 2:0:0:0 sdc 8:32 active ready running 此时在 /dev/mapper 下能发现名为 32017001378a8a9ff 的存储设备(该名字定义为 World Wide Identifier,即 WWID )。 使用命令 `iptables -I OUTPUT -o eth0 -d 192.168.2.201 -j DROP` drop 本机和 iSCSI target 其中一个 ip 之间的通信,这时可以发现状态变化: :: # multipath -ll 32017001378a8a9ff dm-0 Proware,proIPS size=1.1T features='0' hwhandler='0' wp=rw \`-+- policy='round-robin 0' prio=1 status=active |- 2:0:0:0 sdc 8:32 active faulty running \`- 1:0:0:0 sdb 8:16 active ready running # multipath -ll 32017001378a8a9ff dm-0 Proware,proIPS size=1.1T features='0' hwhandler='0' wp=rw \`-+- policy='round-robin 0' prio=1 status=active |- 2:0:0:0 sdc 8:32 failed faulty running \`- 1:0:0:0 sdb 8:16 active ready running dmesg 亦能看到相信的信息: :: [ 5260.772369] sd 2:0:0:0: rejecting I/O to offline device [ 5260.772727] sd 2:0:0:0: [sdc] killing request [ 5260.772732] sd 2:0:0:0: rejecting I/O to offline device [ 5260.773082] sd 2:0:0:0: [sdc] killing request [ 5260.773084] sd 2:0:0:0: rejecting I/O to offline device [ 5260.773434] sd 2:0:0:0: [sdc] killing request [ 5260.773448] sd 2:0:0:0: [sdc] Unhandled error code [ 5260.773449] sd 2:0:0:0: [sdc] [ 5260.773451] Result: hostbyte=0x01 driverbyte=0x00 [ 5260.773453] sd 2:0:0:0: [sdc] CDB: [ 5260.773455] cdb[0]=0x28: 28 00 00 00 00 00 00 00 08 00 [ 5260.773463] end_request: I/O error, dev sdc, sector 0 [ 5260.773819] sd 2:0:0:0: [sdc] Unhandled error code [ 5260.773821] sd 2:0:0:0: [sdc] [ 5260.773822] Result: hostbyte=0x01 driverbyte=0x00 [ 5260.773824] sd 2:0:0:0: [sdc] CDB: [ 5260.773825] cdb[0]=0x28: 28 00 00 00 00 00 00 00 08 00 [ 5260.773831] end_request: I/O error, dev sdc, sector 0 [ 5260.774186] sd 2:0:0:0: [sdc] Unhandled error code [ 5260.774187] sd 2:0:0:0: [sdc] [ 5260.774188] Result: hostbyte=0x01 driverbyte=0x00 [ 5260.774190] sd 2:0:0:0: [sdc] CDB: [ 5260.774191] cdb[0]=0x2a: 2a 00 00 01 2a e0 00 00 08 00 [ 5260.774197] end_request: I/O error, dev sdc, sector 76512 [ 5260.774562] device-mapper: multipath: Failing path 8:32. syslog 的信息(后面两条信息为恢复通信后的输出): :: multipathd: iscsi_data: sdc - directio checker reports path is up multipathd: 8:32: reinstated multipathd: iscsi_data: remaining active paths: 2 编辑 multipath 配置文件 /etc/multipath.conf,内容如下: :: defaults { udev_dir /dev polling_interval 5 selector "round-robin 0" path_grouping_policy multibus getuid_callout "/lib/udev/scsi_id --whitelisted --device=/dev/%n" prio_callout /bin/true path_checker directio prio const rr_min_io 100 rr_weight priorities failback immediate no_path_retry fail user_friendly_name yes } blacklist { devnode "^(ram|sda|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*" devnode "^hd[a-z][[0-9]*]" devnode "^vd[a-z]" devnode "^cciss!c[0-9]d[0-9]*[p[0-9]*]" } multipaths { multipath { wwid 32017001378a8a9ff alias iscsi_data } } 注意 blacklist 部分,其目的是把本地存储设备排除在 multipath 外。在 multipaths 部分,wwid 在 multipath 命令的输出中能看到,alias 为别名。 重启 multipath 服务后,能看到 /dev/mapper 下出现名为 iscsi_data 的存储设备。 之后的操作使用 /dev/mapper/iscsi_data (而不是 /dev/sdb 或 /dev/sdc) 即可利用到 multipath 功能。