具有GPT分区的iSCSI多路径设备的在线调整大小。
不需要重新启动服务器，但是需要卸载该分区并且不使用该分区。

在SAN上调整LUN大小之前

抓取一些数据。
我们的多路径设备是mpatham，大小为20GB。
我们会将其扩展10GB到30GB。

# multipath -ll mpatham
mpatham (36000eb3959dd493f000000000001c3db) dm-77 LEFTHAND,iSCSIDisk
size=20G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 93:0:0:0 sdbt 68:112 active ready running
  `- 94:0:0:0 sdbu 68:128 active ready running

# parted /dev/mapper/mpatham print
Model: Linux device-mapper (multipath) (dm)
Disk /dev/mapper/mpatham: 21.5GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number  Start   End     Size    File system  Name     Flags
 1      1049kB  21.5GB  21.5GB  ext4         primary

# blockdev --getsz /dev/mapper/mpatham
41943040
# blockdev --getsz /dev/mapper/mpathamp1
41940959

# blockdev --getsz /dev/sdbt
41943040
# blockdev --getsz /dev/sdbt1
41940959

# blockdev --getsz /dev/sdbu
41943040
# blockdev --getsz /dev/sdbu1
41940959

# df -h|egrep "File|mpathamp1|data"
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/mpathamp1
                       20G  142M   20G   1% /data

在SAN上调整LUN的大小之后

Parted

我们应该已经在CentOS 6系统上安装了parted。
如果不是这种情况，请运行以下命令：

# yum install parted

重新扫描设备

我们可以重新扫描sdbt和sdbu设备，也可以重新扫描所有正在运行的会话。

重新扫描设备：

# echo 1 > /sys/block/sdbt/device/rescan
# echo 1 > /sys/block/sdbu/device/rescan

或者，重新扫描所有正在运行的会话：

# iscsiadm -m session --rescan

请注意，如果要创建新设备而不是扩展现有设备，则可能需要扫描SAN并登录到所有发现的目标：

# iscsiadm -m discovery -t sendtargets -p netappsan.local:3260
# iscsiadm -m node -L automatic

重新加载多路径服务以获取新的大小：

# /etc/init.d/multipathd reload

多路径设备大小为30GB。

# multipath -ll mpatham
mpatham (36000eb3959dd493f000000000001c3db) dm-77 LEFTHAND,iSCSIDisk
size=30G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 93:0:0:0 sdbt 68:112 active ready running
  `- 94:0:0:0 sdbu 68:128 active ready running

# blockdev --getsz /dev/mapper/mpatham
62914560
# blockdev --getsz /dev/mapper/mpathamp1
41940959

# blockdev --getsz /dev/sdbt
62914560
# blockdev --getsz /dev/sdbt1
41940959

# blockdev --getsz /dev/sdbu
62914560
# blockdev --getsz /dev/sdbu1
41940959

重新创建GPT分区

确保未安装多路径设备：

# umount /dev/mapper/mpathamp1

在多路径设备上分开运行：

# parted /dev/mapper/mpatham
GNU Parted 2.1
Using /dev/mapper/mpatham
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p
Error: The backup GPT table is not at the end of the disk, as it should be.  This might mean that another operating
system believes the disk is smaller.  Fix, by moving the backup to the end (and removing the old backup)?
Fix/Ignore/Cancel? Fix
Warning: Not all of the space available to /dev/mapper/mpatham appears to be used, you can fix the GPT to use all of the
space (an extra 20971520 blocks) or continue with the current setting?
Fix/Ignore? Fix
Model: Linux device-mapper (multipath) (dm)
Disk /dev/mapper/mpatham: 32.2GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number  Start   End     Size    File system  Name     Flags
 1      1049kB  21.5GB  21.5GB  ext4         primary
(parted) rm 1
(parted) unit Kb
(parted) mkpart primary ext4 1049 -1
Warning: You requested a partition from 1049kB to 32212254kB.
The closest location we can manage is 1049kB to 32212237kB.
Is this still acceptable to you?
Yes/No? Yes
(parted) p
Model: Linux device-mapper (multipath) (dm)
Disk /dev/mapper/mpatham: 32212255kB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number  Start   End         Size        File system  Name     Flags
 1      1049kB  32212238kB  32211189kB  ext4         primary
(parted) q

重新加载分区表并调整文件系统大小

告诉内核重新加载分区表。
请注意，在RHEL 6中，partprobe仅会触发操作系统更新磁盘上未使用任何分区的分区。
如果正在使用磁盘上的任何分区，则partprobe不会触发OS更新系统中的分区，因为在某些情况下它被认为是不安全的。

# partprobe

调整大小之前，请检查文件系统：

# e2fsck -f /dev/mapper/mpathamp1
e2fsck 1.41.12 (17-May-2010)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/mapper/mpathamp1: 11/1310720 files (0.0% non-contiguous), 118545/5242619 blocks

调整文件系统大小：

# resize2fs /dev/mapper/mpathamp1
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/mapper/mpathamp1 to 7864059 (4k) blocks.
The filesystem on /dev/mapper/mpathamp1 is now 7864059 blocks long.

抓取一些数据：

# blockdev --getsz /dev/mapper/mpatham
62914560
# blockdev --getsz /dev/mapper/mpathamp1
62912479

# blockdev --getsz /dev/sdbt
62914560
# blockdev --getsz /dev/sdbt1
62912479

# blockdev --getsz /dev/sdbu
62914560
# blockdev --getsz /dev/sdbu1
62912479

最后，安装分区：

# mount /dev/mapper/mpathamp1 /data/

# df -h|egrep "File|mpathamp1|data"
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/mpathamp1
                       30G  142M   30G   1% /data