重新開機後無法識別 PowerFlex 檔案系統

案例

• 在 ScaleIO 裝置上建立檔案系統 （scinia， sinib,...）
• 在 /dev/scinia 上掛載檔案系統
• 將伺服器重新開機 

症狀

重新開機後，使用者無法掛接檔案系統。

當伺服器完成重新啟動時，我無法掛載文件系統，也無法使用 fsck 修復它。

# mount /dev/scinia /mnt
mount: you must specify the filesystem type
# mount -t ext4 /dev/scinia /mnt
mount: wrong fs type, bad option, bad superblock on /dev/scinia,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try

       dmesg | tail  or so



# fsck /dev/scinia
fsck from util-linux-ng 2.17.2
e2fsck 1.41.12 (17-May-2010)
fsck.ext4: Superblock invalid, trying backup blocks...
fsck.ext4: Bad magic number in super-block while trying to open /dev/scinia

The superblock could not be read or does not describe a correct ext2
filesystem.  If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:   e2fsck -b 8193 

#  e2fsck -b 8193 /dev/scinia
e2fsck 1.41.12 (17-May-2010)
e2fsck: Bad magic number in super-block while trying to open /dev/scinia

The superblock could not be read or does not describe a correct ext2
filesystem.  If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:

       e2fsck -b 8193 <device>not 

在 /var/log/messages 中：

[Reboot occurred here]

Dec 18 13:15:48 e8c4-dl360g7-01 kernel: ECS R1_20:Created device scinia (16,0). Capacity 33554432 LB
Dec 18 13:15:48 e8c4-dl360g7-01 kernel: scinia: unknown partition table
Dec 18 13:25:21 e8c4-dl360g7-01 kernel: EXT4-fs (scinia): VFS: Can't find ext4 filesystem
Dec 18 13:26:58 e8c4-dl360g7-01 kernel: EXT4-fs (scinia): VFS: Can't find ext4 filesystem
Dec 18 13:27:11 e8c4-dl360g7-01 kernel: EXT4-fs (scinia): VFS: Can't find ext4 filesystem
Dec 18 13:28:30 e8c4-dl360g7-01 kernel: EXT4-fs (scinia): VFS: Can't find ext4 filesystem
Dec 18 13:33:26 e8c4-dl360g7-01 kernel: EXT4-fs (scinia): VFS: Can't find ext4 filesystem
Dec 18 13:34:07 e8c4-dl360g7-01 kernel: EXT4-fs (scinia): VFS: Can't find ext4 filesystem
Dec 18 16:11:00 e8c4-dl360g7-01 kernel: ECS R1_20:Created device scinia (16,0). Capacity 33554432 LB
Dec 18 16:11:00 e8c4-dl360g7-01 kernel: scinia: unknown partition table
Dec 18 16:11:00 e8c4-dl360g7-01 kernel: EXT4-fs (scinia): VFS: Can't find ext4 filesystem

影響

檔案系統看起來無法使用且已損毀。

當 Linux 在重新啟動後啟動時，它開始掃描設備並按順序自動將字母分配給設備（首先他找到 - 獲取第一個字母）。通常，當使用者未更改任何內容時，重新啟動后，設備將提供相同的設備名稱，但是，有時設備名稱可能會更改，並分配給其他設備。

如果使用者將其檔案系統掛載到 /dev/sciniX 而不是設備的 UUID，他可以認為檔案系統已損壞，但它被分配給了其他設備名稱。這是 Linux 問題，不僅與 ScaleIO 相關。 

範例：使用者有 10 台設備，然後他將其減少到 5 台，並在一天后重新啟動。您可以看到，指派給 scinia 的裝置後來又指派給了不同的裝置。 

17^日（從10台減少到5台設備后）

在伺服器-01 上

# ls -l /dev/disk/by-id/scaleio*

lrwxrwxrwx 1 root root 12 Dec 17 12:00 /dev/disk/by-id/scaleio-vol-376584c0169c4216-49ff9f7a0000000c -> ../../scinij
lrwxrwxrwx 1 root root 12 Dec 17 12:00 /dev/disk/by-id/scaleio-vol-376584c0169c4216-49ff9f7b0000000d -> ../../scinib
lrwxrwxrwx 1 root root 12 Dec 17 12:00 /dev/disk/by-id/scaleio-vol-376584c0169c4216-49ff9f7c0000000e -> ../../scinii
lrwxrwxrwx 1 root root 12 Dec 17 12:00 /dev/disk/by-id/scaleio-vol-376584c0169c4216-49ff9f7d0000000f -> ../../scinia
lrwxrwxrwx 1 root root 12 Dec 17 12:00 /dev/disk/by-id/scaleio-vol-376584c0169c4216-49ff9f7e00000010 -> ../../scinih

現在：即在 18 日重新開機後，檔案系統 （FS） 「消失」

ls -l /dev/disk/by-id/scaleio*

lrwxrwxrwx 1 root root 12 Dec 19 10:51 /dev/disk/by-id/scaleio-vol-376584c0169c4216-49ff9f7a0000000c -> ../../scinia
lrwxrwxrwx 1 root root 12 Dec 19 10:24 /dev/disk/by-id/scaleio-vol-376584c0169c4216-49ff9f7b0000000d -> ../../scinid
lrwxrwxrwx 1 root root 12 Dec 19 10:24 /dev/disk/by-id/scaleio-vol-376584c0169c4216-49ff9f7c0000000e -> ../../scinic
lrwxrwxrwx 1 root root 12 Dec 19 10:24 /dev/disk/by-id/scaleio-vol-376584c0169c4216-49ff9f7d0000000f -> ../../scinie
lrwxrwxrwx 1 root root 12 Dec 19 10:33 /dev/disk/by-id/scaleio-vol-376584c0169c4216-49ff9f7e00000010 -> ../../scinib

因應措施

 要求使用者使用 UUID 進行掛接。

 範例：他們應使用裝置 uuid （而非裝置名稱） 對應磁碟區：

ls /dev/disk/by-uuid/      to find out the UUID

fstab 條目的範例：

 UUID=<UUID> <mount point>      ext4 defaults,errors=remount-ro 0 1