Help Center/ Elastic Volume Service/ Best Practices/ Extending Disk Partitions and File Systems (Linux Kernel Earlier Than 3.6.0)/ Preparing for Extending Disk Partitions and File Systems (Linux Kernel Earlier Than 3.6.0)
Updated on 2023-06-21 GMT+08:00
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Preparing for Extending Disk Partitions and File Systems (Linux Kernel Earlier Than 3.6.0)

After a disk has been expanded on the management console, the disk size is enlarged, but the additional space cannot be used directly.

  • Exercise caution when expanding the disk capacity. Incorrect operations may lead to data loss or exceptions. So you are advised to back up the disk data using backups or snapshots before expansion. For details about backups, see Managing EVS Backups. For details about snapshots, see Creating a Snapshot (OBT).
  • If the OS kernel version is earlier than 3.6.0, the extension of an existing MBR partition and file system takes effect only after a system reboot, and services will be interrupted. After you run reboot, the additional space is automatically added to the partition at the end of the system disk.
  • If you do not want to reboot your ECS, you can migrate data from the system disk to a data disk on the same ECS, detach the data disk, and attach it to an ECS whose OS kernel version is later than 3.6.0. In this case, the disk partition and file system can be extended without a reboot. You can then detach and attach back the extended disk to the original ECS, and migrate data back to the system disk. There are risks in migrating data. Back up the data before migration. To extend partitions and file systems on an ECSwhose kernel version is greater than 3.6.0, see Expanding Disk Partitions and File Systems (Linux).

Before extending the disk partition and file system, you must check the disk partition style and file system format, and then select an appropriate operation accordingly.

  1. To view the disk partition style, see the following methods:
  2. To select an appropriate operation, see Table 1.
    Table 1 Disk partition and file system extension scenarios

    Disk

    Scenario

    Method

    System disk

    Create a new MBR partition with the additional space.

    Creating a New MBR Partition

    Allocate the additional space to an existing MBR partition.

    Extending an Existing MBR Partition (Kernel Version Earlier Than 3.6.0)

    Data disk

    Create a new MBR partition with the additional space.

    Creating a New MBR Partition

    Allocate the additional space to an existing MBR partition.

    Extending an Existing MBR Partition

    Create a new GPT partition with the additional space.

    Creating a New GPT Partition

    Allocate the additional space to an existing GPT partition.

    Extending an Existing GPT Partition

    SCSI data disk

    Create a new MBR partition with the additional space.

    Creating a New MBR Partition

    Allocate the additional space to an existing MBR partition.

    Extending an Existing MBR Partition

    The maximum disk capacity that MBR supports is 2 TB, and the disk space exceeding 2 TB cannot be used.

    If your disk uses MBR and you need to expand the disk capacity to over 2 TB, change the partition style from MBR to GPT. Ensure that the disk data has been backed up before changing the partition style because services will be interrupted and data on the disk will be cleared during this change.

Method 1: Check Partition Style and File System Format Using fdisk

  1. Run the following command to view all the disks attached to the server:

    lsblk

    Information similar to the following is displayed: 
    [root@ecs-test-0001 ~]# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
vda    253:0    0   40G  0 disk
└─vda1 253:1    0   40G  0 part /
vdb    253:16   0  150G  0 disk
└─vdb1 253:17   0  100G  0 part /mnt/sdc

    In this example, data disk /dev/vdb already has partition /dev/vdb1 before capacity expansion, and the additional 50 GB added has not been allocated yet. Therefore, /dev/vdb has 150 GB, and /dev/vdb1 has 100 GB.

  2. Run the following command to view the current disk partition style:

    fdisk -l

    Information similar to the following is displayed: 
    [root@ecs-test-0001 ~]# fdisk -l

Disk /dev/vda: 42.9 GB, 42949672960 bytes, 83886080 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: 0x000bcb4e

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048    83886079    41942016   83  Linux

Disk /dev/vdb: 161.1 GB, 161061273600 bytes, 314572800 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: 0x38717fc1

   Device Boot      Start         End      Blocks   Id  System
/dev/vdb1            2048   209715199   104856576   83  Linux

    The value in the System column indicates the disk partition style. Value Linux indicates the MBR partition style. Value GPT indicates the GPT partition style.

    • If the disk partitions displayed are inconsistent with those obtained in 1, the partition that is not displayed uses the GPT partition style and has unallocated space. In this case, you cannot query all the partition information using the fdisk -l command. Go to Method 2: Check Partition Style and File System Format Using parted.
    • If the disk partitions displayed are consistent with those obtained in 1, continue with the following operations.

  3. Run the following command to view the partition's file system format:

    blkid Disk partition

    In this example, run the following command:

    blkid /dev/vdb1

    [root@ecs-test-0001 ~]# blkid /dev/vdb1
/dev/vdb1: UUID="0b3040e2-1367-4abb-841d-ddb0b92693df" TYPE="ext4"

    In the command output, the TYPE value is ext4, indicating that /dev/vdb1's file system format is ext4.

  4. Run the following command to view the file system status:

    ext*: e2fsck -n Disk partition

    xfs: xfs_repair -n Disk partition

    In this example, the ext4 file system is used. Therefore, run the following command:

    e2fsck -n /dev/vdb1

    Information similar to the following is displayed: 
    [root@ecs-test-0001 ~]# e2fsck -n /dev/vdb1
e2fsck 1.42.9 (28-Dec-2013)
Warning!  /dev/vdb1 is mounted.
Warning: skipping journal recovery because doing a read-only filesystem check.
/dev/vdb1: clean, 11/6553600 files, 459544/26214144 blocks

    If the file system status is clean, the file system status is normal. Otherwise, rectify the faulty and then perform the capacity expansion.

Method 2: Check Partition Style and File System Format Using parted

  1. Run the following command to view all the disks attached to the server:

    lsblk

    Information similar to the following is displayed: 
    [root@ecs-test-0001 ~]# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
vda    253:0    0   40G  0 disk
└─vda1 253:1    0   40G  0 part /
vdb    253:16   0  150G  0 disk
└─vdb1 253:17   0  100G  0 part /mnt/sdc

    In this example, data disk /dev/vdb already has partition /dev/vdb1 before capacity expansion, and the additional 50 GB added has not been allocated yet. Therefore, /dev/vdb has 150 GB, and /dev/vdb1 has 100 GB.

  2. Run the following command and enter p to view the disk partition style:

    parted Disk

    For example, run the following command to view /dev/vdb's partition style:

    parted /dev/vdb

    Information similar to the following is displayed: 
    [root@ecs-test-0001 ~]# parted /dev/vdb
GNU Parted 3.1
Using /dev/vdb
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/vdb appears to be used, you can fix the GPT to use all of the space (an extra 104857600
blocks) or continue with the current setting?
Fix/Ignore? Fix
Model: Virtio Block Device (virtblk)
Disk /dev/vdb: 161GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End    Size   File system  Name  Flags
 1      1049kB  107GB  107GB  ext4         test

(parted)
    In the command output, parameter Partition Table indicates the disk partition style. Value msdos indicates the MBR partition style, and value gpt indicates the GPT partition style.
    • If the following error information is displayed, enter Fix. 
      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)?

      The GPT partition table information is stored at the start of the disk. To reduce the risk of damages, a backup of the information is saved at the end of the disk. When you expand the disk capacity, the end of the disk changes accordingly. In this case, enter Fix to move the backup file of the information to new disk end.

    • If the following warning information is displayed, enter Fix. 
      Warning: Not all of the space available to /dev/vdb appears to be used, you can fix the GPT to use all of the space (an extra 104857600
blocks) or continue with the current setting?
Fix/Ignore? Fix

      Enter Fix as prompted. The system automatically sets the GPT partition style for the additional space.

  3. Enter q and press Enter to exit parted.