Ultra-high I/O ECSs

Overview

Ultra-high I/O ECSs use high-performance local NVMe SSDs to provide high storage input/output operations per second (IOPS) and low read/write latency. You can create such ECSs with high-performance local NVMe SSDs attached on the management console.

Scenarios

• Ultra-high I/O ECSs are suitable for high-performance relational databases.
• Ultra-high I/O ECSs are suitable for NoSQL databases (such as Cassandra and MongoDB) and ElasticSearch.

Specifications

Local Disk Performance

Table 2 and Table 3 list the IOPS performance of local disks and specifications of a single local disk attached to an I3 ECS.

Notes

• Ultra-high I/O ECSs support the following OSs:
  • EulerOS 2.2
  • CentOS 7.2
  • CentOS 7.3
  • Ubuntu Server 16.04
  • SUSE Linux Enterprise Server 12 SP2
  • Fedora 25 64bit
  • OpenSUSE 42.2 64bit
  

  EulerOS 2.2 and Ubuntu Server 16.04 are recommended.

• If the host where an ultra-high I/O ECS is deployed is faulty, the ECS cannot be restored through live migration.
  • If the host is faulty or subhealthy, you need to stop the ECS for hardware repair.
  • In case of system maintenance or hardware faults, the ECS will be redeployed (to ensure HA) and cold migrated to another host. The local disk data of the ECS will not be retained.
• Ultra-high I/O ECSs do not support specifications change.
• Ultra-high I/O ECSs do not support local disk snapshots or backups.
• Ultra-high I/O ECSs can use local disks, and can also have EVS disks attached to provide a larger storage size. Note the following when using the two types of storage media:
  • Only an EVS disk, not a local disk, can be used as the system disk of an ultra-high I/O ECS.
  • Both EVS disks and local disks can be used as data disks of an ultra-high I/O ECS.
  • An ultra-high I/O ECS can have a maximum of 60 attached disks (including VBD, SCSI, and local disks). For details about constraints, see Can I Attach Multiple Disks to an ECS?
• Modify the fstab file to set automatic disk mounting at ECS start. For details, see Configuring Automatic Mounting at System Start.
• The local disk data of an ultra-high I/O ECS if an exception occurs, such as physical server breakdown or local disk damage. If your application does not use the data reliability architecture, it is a good practice to use EVS disks to build your ECS.
• When an ultra-high I/O ECS is deleted, the data on local NVMe SSDs will also be automatically deleted, which can take some time. As a result, an ultra-high I/O ECS takes a longer time than other ECSs to be deleted. Back up the data before deleting such an ECS.
• The data reliability of local disks depends on the reliability of physical servers and hard disks, which are SPOF-prone. It is a good practice to use data redundancy mechanisms at the application layer to ensure data availability. Use EVS disks to store service data that needs to be stored for a long time.
• The device name of a local disk attached to an ultra-high I/O ECS is /dev/nvme0n1 or /dev/nvme0n2.
• Local disks attached to Ir3 ECSs can be split for multiple ECSs to use. If a local disk is damaged, the ECSs that use this disk will be affected.

  You are advised to add Ir3 ECSs to an ECS group during the creation process to prevent such failures. For details, see Managing ECS Groups.

• The basic resources, including vCPUs, memory, and image of an ultra-high I/O ECS will continue to be billed after the ECS is stopped. To stop the ECS from being billed, delete it and its associated resources. For more information, see Will Am I Continue to Be Billed After ECSs Are Stopped?

Handling Damaged Local Disks Attached to an ECS of I Series

If a local disk attached to an ECS is damaged, perform the following operations to handle this issue:

For a Linux ECS:

1. Detach the faulty local disk.
   1. Run the following command to query the mount point of the faulty disk:

      df –Th

      Figure 1 Querying the mount point
      
   2. Run the following command to detach the faulty local disk:

      umount Mount point

      In the example shown in Figure 1, the mount point of /dev/nvme0n1 is /mnt/nvme0. Run the following command:

      umount /mnt/nvme0

2. Check whether the mount point of the faulty disk is configured in /etc/fstab of the ECS. If yes, comment out the mount point to prevent the ECS from entering the maintenance mode upon ECS startup after the faulty disk is replaced.
   1. Run the following command to obtain the partition UUID:

      blkid Disk partition

      In this example, run the following command to obtain the UUID of the /dev/nvme0n1 partition:

      blkid /dev/nvme0n1

      Information similar to the following is displayed:

      /dev/nvme0n1: UUID="b9a07b7b-9322-4e05-ab9b-14b8050cd8cc" TYPE="ext4"

   2. Run the following command to check whether /etc/fstab contains the automatic mounting information about the disk partition:

      cat /etc/fstab

      Information similar to the following is displayed:

      UUID=b9a07b7b-9322-4e05-ab9b-14b8050cd8cc    /mnt   ext4    defaults        0 0

   3. If the mounting information exists, perform the following steps to delete it.
      1. Run the following command to edit /etc/fstab:

         vi /etc/fstab

         Use the UUID obtained in 2.a to check whether the mounting information of the local disk is contained in /etc/fstab. If yes, comment out the information. This prevents the ECS from entering the maintenance mode upon ECS startup after the local disk is replaced.

      2. Press i to enter editing mode.
      3. Delete or comment out the automatic mounting information of the disk partition.

         For example, add a pound sign (#) at the beginning of the following command line to comment out the automatic mounting information:

         # UUID=b9a07b7b-9322-4e05-ab9b-14b8050cd8cc    /mnt   ext4    defaults        0 0

      4. Press Esc to exit editing mode. Enter :wq and press Enter to save the settings and exit.
3. Run the following command to obtain the SN of the local disk:

   For example, if the nvme0n1 disk is faulty, obtain the serial number of the nvme0n1 disk.

   ll /dev/disk/by-id/

   Figure 2 Querying the serial number of the faulty local disk
   
4. Stop the ECS and provide the serial number of the faulty disk to technical support personnel to replace the local disk.

   After the local disk is replaced, restart the ECS to synchronize the new local disk information to the virtualization layer.

For a Windows ECS:

1. Open Computer Management, choose Computer Management (Local) > Storage > Disk Management, and view the disk ID, for example, Disk 1.
2. Open Windows PowerShell as an administrator and run the following command to query the disk on which the logical disk is created:

   Get-CimInstance -ClassName Win32_LogicalDiskToPartition |select Antecedent, Dependent | fl

   Figure 3 Querying the disk on which the logical disk is created
   
3. Run the following command to obtain the serial number of the faulty disk according to the mapping between the disk ID and serial number:

   Get-Disk | select Number, SerialNumber

   Figure 4 Querying the mapping between the disk ID and serial number
   
   

   If the serial number cannot be obtained by running the preceding command, see Using a Serial Number to Obtain the Disk Device Name (Windows).

4. Stop the ECS and provide the serial number of the faulty disk to technical support personnel to replace the local disk.

   After the local disk is replaced, restart the ECS to synchronize the new local disk information to the virtualization layer.