群晖系统盘md0扩容

0x01 前言

博主的一台黑群晖是从 DSM 6 一路升级到 DSM 7.2 的。最近 DSM 7.3 发布，本想顺手升级，结果系统升级却一直报错提示“系统空间不足”。

SSH 登录进系统后，用 df -h 一看，发现根目录 /dev/md0（群晖的系统盘）使用率已经爆满了，扩容根目录可能需要动分区表；而且群晖的磁盘结构中，md0（系统分区）后面紧接着就是 md1（Swap 交换分区），这就意味着物理扇区是连续占用的，强行调整分区边界风险极大，理论上非常难扩容。

但是在网上突然看到一篇文章：群晖md0分区无损扩容教程，用于解决从DSM6升级到7后md0分区大小仍然是2.4GB 我发现了一个“意外惊喜”：其实底层物理磁盘的系统分区（p1）已经被分配了 8GB 的空间，只是上层的 RAID 阵列（md0）依然维持在 DSM 6 时代的 2.4GB 大小！ 也就是说，我们根本不需要冒着风险去改动底层的物理分区表，只需要把上层限制了大小的 RAID 阵列和文件系统“释放”出来，填满那闲置的 8GB 空间即可。

0x02 扩容

可以看到md0 群晖系统盘 只有2898114624 blocks（约等于 2.4GB）成员组是sata2p1[12] sata6p1[16] sata5p1[13] sata4p1[15] sata3p1[14]

root@SA6400:/# cat /proc/mdstat
Personalities : [raid1] [raid6] [raid5] [raid4] [raidF1]
md2 : active raid5 sata2p3[4] sata5p3[5] sata4p3[2] sata3p3[1]
      2898114624 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/4] [UUUU]

md3 : active raid1 sata6p3[0]
      5849798208 blocks super 1.2 [1/1] [U]

md1 : active raid1 sata2p2[12] sata6p2[16] sata4p2[15] sata5p2[13] sata3p2[14]
      2096128 blocks super 1.2 [12/5] [UUUUU_______]

md0 : active raid1 sata2p1[12] sata6p1[16] sata5p1[13] sata4p1[15] sata3p1[14]
      2489216 blocks super 1.2 [12/5] [UUUUU_______]

unused devices: <none>

查看所有物理设备，虽然每个物理分区 p1 确实是 8GB（16,777,216 sectors × 512 bytes），但 RAID 阵列没有使用分区的全部空间。

# 可以看到 sata2p1 sata6p1 sata5p1 sata4p1 sata3p1 其实都是8G
root@SA6400:/#  fdisk -l /dev/sata?
Disk /dev/sata2: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: ST1000DM010-2EP102
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x41f2b7ea

Device       Boot    Start        End    Sectors   Size Id Type
/dev/sata2p1          8192   16785407   16777216     8G fd Linux raid autodetect
/dev/sata2p2      16785408   20979711    4194304     2G fd Linux raid autodetect
/dev/sata2p3      21241856 1953320351 1932078496 921.3G fd Linux raid autodetect

Disk /dev/sata3: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: ST1000DM010-2EP102
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0xedcbbbac

Device       Boot    Start        End    Sectors   Size Id Type
/dev/sata3p1          8192   16785407   16777216     8G fd Linux raid autodetect
/dev/sata3p2      16785408   20979711    4194304     2G fd Linux raid autodetect
/dev/sata3p3      21241856 1953320351 1932078496 921.3G fd Linux raid autodetect

Disk /dev/sata4: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: ST1000DM010-2EP102
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0xbdcf33c5

Device       Boot    Start        End    Sectors   Size Id Type
/dev/sata4p1          8192   16785407   16777216     8G fd Linux raid autodetect
/dev/sata4p2      16785408   20979711    4194304     2G fd Linux raid autodetect
/dev/sata4p3      21241856 1953320351 1932078496 921.3G fd Linux raid autodetect

Disk /dev/sata5: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: ST1000DM010-2EP102
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0xbcd081e2

Device       Boot    Start        End    Sectors   Size Id Type
/dev/sata5p1          8192   16785407   16777216     8G fd Linux raid autodetect
/dev/sata5p2      16785408   20979711    4194304     2G fd Linux raid autodetect
/dev/sata5p3      21241856 1953320351 1932078496 921.3G fd Linux raid autodetect

Disk /dev/sata6: 5.5 TiB, 6001175126016 bytes, 11721045168 sectors
Disk model: HUS726T6TALE6L4
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: C9209603-1534-426C-9CFA-9BEFFE39C89F

Device          Start         End     Sectors  Size Type
/dev/sata6p1     8192    16785407    16777216    8G Linux RAID
/dev/sata6p2 16785408    20979711     4194304    2G Linux RAID
/dev/sata6p3 21241856 11720840351 11699598496  5.5T Linux RAID

那就直接开始扩容

# 调整md0到最大可用容量
root@SA6400:/# mdadm --grow /dev/md0 --size=max
mdadm: component size of /dev/md0 has been set to 8387584K
# 扩容文件系统
root@SA6400:/# resize2fs /dev/md0
resize2fs 1.44.1 (24-Mar-2018)
Filesystem at /dev/md0 is mounted on /; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on /dev/md0 is now 2096896 (4k) blocks long.
# 可以看到已经生效， 现在 8,387,584 blocks  (~8GB) ，等 resync 完成后检查
root@SA6400:/# cat /proc/mdstat
Personalities : [raid1] [raid6] [raid5] [raid4] [raidF1]
md2 : active raid5 sata2p3[4] sata5p3[5] sata4p3[2] sata3p3[1]
      2898114624 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/4] [UUUU]

md3 : active raid1 sata6p3[0]
      5849798208 blocks super 1.2 [1/1] [U]

md1 : active raid1 sata2p2[12] sata6p2[16] sata4p2[15] sata5p2[13] sata3p2[14]
      2096128 blocks super 1.2 [12/5] [UUUUU_______]

md0 : active raid1 sata2p1[12] sata6p1[16] sata5p1[13] sata4p1[15] sata3p1[14]
      8387584 blocks super 1.2 [12/5] [UUUUU_______]
      [==========>..........]  resync = 50.4% (4235392/8387584) finish=0.8min speed=79371K/sec

unused devices: <none>
# 完成
root@SA6400:/# df -h
Filesystem              Size  Used Avail Use% Mounted on
/dev/md0                7.9G  1.6G  5.9G  22% /