Elastic Cloud Disk
An elastic cloud disk is a cloud disk with an independent lifecycle (billing cycle) that can be freely attached to and detached from different CVM instances in the same region and availability zone. Currently, an elastic cloud disk cannot be attached to multiple CVM instances.
Non-Elastic Cloud Disk
A non-elastic cloud disk is a cloud disk that is created together with the CVM and whose lifecycle depends on the CVM. A non-elastic cloud disk does not support elastic attachment.
GPT
Rollback
It refers to the operation used to restore a program or data to its last correct status when program or data processing error occurs. Rollback includes program rollback and data rollback.
IOPS
Input/Output Per Second (IOPS) is the number of input/output operations (or read-write operations) per second, one of the key metrics for measuring hard disk performance. IOPS refers to the number of I/O requests that a system can process per unit of time, usually measured in the number of I/O requests processed per second. I/O requests are usually read or write data operation requests.
Traditional disks are essentially mechanical devices, such as FC, SAS, and SATA disks, with rotational speeds of 5,400/7,200/10,000/15,000 rpm. The key factor affecting disk performance is disk service time, the time it takes for a disk to complete an I/O request. Disk service time consists of three parts: seek time, rotational latency, and data transfer time.
Typically, a single mechanical hard disk with a rotational speed of 7200 rpm provides 75 to 150 IOPS, while a single mechanical hard disk with a rotational speed of 15000 rpm provides 175 to 210 IOPS. The specific values depend on factors such as access patterns (for example, sequential or random) and I/O size.
Snapshot Chain
Snapshot chain refers to the relationship chain composed of all snapshots on the same disk, and each node represents a snapshot of the disk.
MBR
See Master Boot Record Partitioning.
Guid Partition Table
The Guid Partition Table (GPT) is a partition structure of the physical hard disk, which is part of the Extensible Firmware Interface (EFI) standard and used to replace the MBR partition table of most existing disks.
Full Snapshot
It refers to the snapshot for disk data created for the first time, and it saves the full amount of disk data.
Sequential I/O
Sequential I/O refers to read/write operations that successively access data from adjacent addresses and is performed one by one on a logical block basis. With sequential I/O access, the seek time of hard disk is greatly reduced because the read-write heads rarely need to move to access the next block. Most services, such as data backup and log flow, generate sequential I/O.
Random I/O
Random I/O refers to that access address is not continuous, but randomly distributed in the addressing space of disk LUNs. The services that mainly generate random I/O include: OLTP service, SQL and instant messaging service.
Striping
Striping is a technique that automatically balances the load of I/O across multiple physical disks.
Throughput
It refers to the quantity of data successfully transmitted per unit time for the network, device, port, virtual circuit or other facilities.
Cloud Disk Snapshot
It saves a replica of the cloud disk at a certain point, and can be used to restore the cloud disk to the state when the snapshot was created.
Incremental Snapshot
Incremental snapshot refers to the snapshot where only the files added or modified compared with the previous one need to be backed up for each subsequent snapshot after the full snapshot or the previous incremental snapshot.
Main Boot Record
The Main Boot Record (MBR), also known as the main boot sector, is the first sector that must be read when accessing the hard disk after the computer is started. The main boot sector records the relevant information of the hard disk itself and the size and location information of each partition of the hard disk, and is also an important entrance for data information.