Quickly Creating an EVS Disk and Using It on a Linux Server

Scenarios

You can use EVS disks as system disks or data disks. System disks are created together with servers, while data disks can be created together with servers or separately. If you have created data disks separately, you must attach and initialize them before they can be used.

This section describes how a non-shared data disk can be created on the EVS console, attached to a Linux server, and initialized on the server.

Operation Process

Procedure	Description
Step 1: Create an EVS Disk	Create a data disk on the EVS console.
Step 2: Attach the EVS Disk	Attach the data disk to a Linux server.
Step 3: Initialize the EVS Disk	Initialize the data disk on the server.

Step 1: Create an EVS Disk

Go to the Create Disk page.
1. Log in to the console.
2. Click in the upper left corner of the page and choose Storage > Elastic Volume Service.
3. Click Create Disk in the upper right corner.

Configure mandatory parameters based on the following table and retain the default settings for other parameters.

Parameter	Example Value	Description
Region		Resources are region-specific and cannot be used across regions through internal network connections. For low network latency and quick resource access, select the nearest region.
AZ	-	You can only attach EVS disks to servers in the same AZ. After a disk is created, its AZ cannot be changed.
Data Source	Do not configure it.	If you want to create an empty data disk, do not configure a data source.
Disk Type	Ultra-high I/O	To learn more about disk types, see Disk Types and Performance.
Capacity	100 GiB	Enter a disk capacity.
Automatic Backup	Do not use	Automatic backup allows you to back up the disk data to ensure your data security and integrity.
More > Share	Do not selection this option.	A non-shared disk can only be attached to one server. The sharing attribute of a disk cannot be changed after the disk has been created.
More > SCSI	Select this option.	A SCSI disk allows the server OS to directly access the underlying storage media and send SCSI commands to the disk. The device type of a disk cannot be changed after the disk has been created.
More > Encryption	Select this option and use the default key.	EVS uses the industry-standard XTS-AES-256 cryptographic algorithm and keys to encrypt EVS disks. The encryption attribute of a disk cannot be changed after the disk has been created.
Disk Name	volume-0001	Enter a disk name.
Quantity	1	The preset disk quantity is 1, which means only one disk is created.

Click Apply Now.
Go back to the disk list page. When the status of the volume-0001 disk changes to In-use, the disk is successfully created.

Step 2: Attach the EVS Disk

EVS disks cannot be used alone. You need to attach them to cloud servers first.

In the disk list, find the volume-0001 disk and click Attach in the Operation column.
Attach the volume-0001 disk to your desired server. Ensure that the server and disk are in the same AZ.
Click OK to go back to the disk list page. When the status of the volume-0001 disk changes to In-use, the disk is successfully attached.

Step 3: Initialize the EVS Disk

After attaching the volume-0001 disk, you need to initialize it before it can be used. The following example uses fdisk to format the disk into two primary MBR partitions, with one 40 GiB and the other 60 GiB.

Log in to the server.
For how to log in to an ECS, see the Elastic Cloud Server User Guide.
Create two primary partitions, /dev/vdb1 and /dev/vdb2 for data disk /dev/vdb.
1. Check that the capacity of the /dev/vdb data disk is 100 GiB.
  lsblk
```
[root@ecs-centos76 ~]# lsblk
NAME   MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda    253:0    0  40G  0 disk
├vda1 253:1    0   1G  0 part /boot
└vda2 253:2    0  39G  0 part /
vdb    253:16   0  100G 0 disk
```
  Note
  In the command output, disk /dev/vda is partitioned, but disk /dev/vdb is not.
1. Create the first primary partition /dev/vdb1.
  fdisk /dev/vdb
  
  n
  
  p
  
  1
  Note
  Entering p for Partition type creates a primary partition, and entering e creates an extended partition.
  Value 1 is the primary partition number.
```
[root@ecs-test-0001 ~]# fdisk /dev/vdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0x38717fc1.

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p
Partition number (1-4, default 1): 1
```
2. Set First sector to 2048 and Last sector to 83886079 for partition /dev/vdb1 (40 GiB).
  Note
  First and last sectors of the partitions in this example are calculated as follows:
  
  Value of sectors = Capacity/512 bytes, 1 GiB = 1073741824 bytes
  
  First sector (2048-209715199, default 2048) shows the sector value range of the /dev/vdb data disk (100 GiB).
  First sector = 2048
  
  Last sector = Value of sectors – 1 = (100 x 1073741824/512) – 1 = 209715200 – 1=209715199
  
  For the first partition /dev/vdb1 (40 GiB) of the /dev/vdb data disk:
  First sector = 2048 (The first sector of the /dev/vdb data disk is used.)
  
  Last sector = Value of sectors – 1 = (40 x 1073741824/512) – 1 = 83886079
  
  For the second partition /dev/vdb2 (60 GiB) of the /dev/vdb data disk:
  First sector = Last sector of /dev/vdb1 + 1 = 83886079 + 1 = 83886080
  
  Last sector = First sector + Value of sectors – 1 = 83886080 + (60 x 1073741824/512) – 1 = 209715199
```
First sector (2048-209715199, default 2048): 2048
Last sector, +sectors or +size{K,M,G} (2048-209715199, default 209715199):83886079
Partition 1 of type Linux and of size 40 GB is set
```
1. Create the second primary partition /dev/vdb2.
  n
  
  p
  
  2
```
Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p
Partition number (1-4, default 2): 2
```
2. Set the First sector to 83886080 and Last sector to 209715199 for partition /dev/vdb2.
```
First sector (83886080-209715199, default 83886080): 83886080
Last sector, +sectors or +size{K,M,G} (83886080-209715199, default 209715199):209715199
Partition 2 of type Linux and of size 60 GB is set
```

Check the sizes and partition styles of the new partitions.

Check whether the partitioning is successful.

Command (m for help): p

Disk /dev/vdb: 107.4 GB, 107374182400 bytes, 209715200 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: 0x994727e5

   Device Boot       Start         End      Blocks   Id  System
/dev/vdb1             2048    83886079    41942016   83  Linux
/dev/vdb2         83886080   209715199    62914560   83  Linux

Command (m for help):

Note

In case that you want to discard the changes made before, you can exit fdisk by entering q and press Enter. Then, re-create the partitions by referring to step 1.

Write the changes to the partition table and synchronize the new partition table to the OS.
w

partprobe

Note
If error message -bash: partprobe: command not found is returned, the system cannot identify the command. In this case, run yum install -y parted to install the command. Then run the command again.

Confirm that the partition style is MBR.

parted /dev/vdb

Note

If Partition Table: msdos is returned, the partition style is MBR.

[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
Model: Virtio Block Device (virtblk)
Disk /dev/vdb: 107GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number  Start   End      Size     Type     File system  Flags
 1      1049kB  42.9GB   42.9GB   primary
 2      42.9GB  107GB    64.4GB   primary             

(parted) q
[root@ecs-test-0001 ~]#

Enter q and press Enter to exit parted.

Create ext4 file systems for partitions /dev/vdb1 (40 GiB) and /dev/vdb2 (60 GiB).

mkfs -t ext4 /dev/vdb1

mkfs -t ext4 /dev/vdb2

Note

It takes some time to create file systems. Do not exit before the system returns the following information:

[root@ecs-test-0001 ~]# mkfs -t ext4 /dev/vdb1
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
2621440 inodes, 10485504 blocks
524275 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2157969408
320 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

Check whether the file system format is ext4.

parted /dev/vdb

[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
Model: Virtio Block Device (virtblk)
Disk /dev/vdb: 107GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number  Start   End      Size     Type     File system  Flags
 1      1049kB  42.9GB   42.9GB   primary  ext4
 2      42.9GB  107GB    64.4GB   primary  ext4            

(parted) q
[root@ecs-test-0001 ~]#

Enter q and press Enter to exit parted.

Create directories (mount points) and mount the new partitions on the created mount points.
mkdir -p /mnt/sdc

mkdir -p /mnt/sdd

mount /dev/vdb1 /mnt/sdc

mount /dev/vdb2 /mnt/sdd

lsblk

View the mount results.
```
[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 100G  0 disk
├vdb1 253:17   0  40G  0 part /mnt/sdc
├vdb2 253:18   0  60G  0 part /mnt/sdd
```
You should now see that partitions /dev/vdb1 and /dev/vdb2 are mounted on /mnt/sdc and /mnt/sdd.

Use the partition UUIDs to configure auto mount at startup.

Note

Mounts become invalid after a system reboot. You can configure auto mount at startup by adding information of the new partition into the /etc/fstab file.
You are advised not to use device names to identify disks in the /etc/fstab file because device names are assigned dynamically and may change (for example, from /dev/vdb1 to /dev/vdb2) after a stop or start. This can even prevent your server from booting up.
UUIDs are the unique character strings for identifying partitions in Linux.
This operation will not affect the existing data on the ECS.

Query the partition UUIDs.
blkid /dev/vdb1

blkid /dev/vdb2
```
[root@ecs-test-0001 ~]# blkid /dev/vdb1
/dev/vdb1: UUID="0b3040e2-1367-4abb-841d-ddb0b92693df" TYPE="ext4"
/dev/vdb2: UUID="0d6769k2-1745-9dsf-453d-hgd0b34267dj" TYPE="ext4"
```
The UUIDs of partitions /dev/vdb1 and /dev/vdb2 are 0b3040e2-1367-4abb-841d-ddb0b92693df and 0d6769k2-1745-9dsf-453d-hgd0b34267dj.

Configure auto mount at startup.

vi /etc/fstab

Press i to enter the editing mode, move the cursor to the end of the file, press Enter, and add the following content:

UUID=0b3040e2-1367-4abb-841d-ddb0b92693df    /mnt/sdc     ext4    defaults     0    2
UUID=0d6769k2-1745-9dsf-453d-hgd0b34267dj    /mnt/sdd     ext4    defaults     0    2

Press Esc, enter :wq, and press Enter to save the settings and exit the vi editor.

Table 1 Parameter description
Example Value	Description
UUID=0b3040e2-1367-4abb-841d-ddb0b92693df	The UUID of the partition.
/mnt/sdc	The mount point of the partition.
ext4	The file system format of the partition.
defaults	The partition mount option. Normally, this parameter is set to defaults.
0	The Linux dump backup option. 0: Linux dump backup is not used. Usually, dump backup is not used, and you can set this parameter to 0. 1: Linux dump backup is used.
2	The fsck option, which means whether to use fsck to check the disk during startup. 2: The check starts from the partitions whose mount points are non-root directories. / is the root directory. 1: The check starts from the partitions whose mount points are root directories. 0: The fsck option is not used.

Verify that auto mount takes effect.
umount /dev/vdb1

umount /dev/vdb2

mount -a

The system reloads all the content in the /etc/fstab file.

Query file system mounting information.

mount | grep /mnt/sdc

mount | grep /mnt/sdd

If information similar to the following is displayed, auto mount has taken effect:
```
root@ecs-test-0001 ~]# mount | grep /mnt/sdc
/dev/vdb1 on /mnt/sdc type ext4 (rw,relatime,data=ordered)
root@ecs-test-0001 ~]# mount | grep /mnt/sdd
/dev/vdb2 on /mnt/sdd type ext4 (rw,relatime,data=ordered)
```

You can use the disk after it is initialized.

Parent topic: Getting Started

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