Volumes are logical devices and they are allocated to compute nodes.
The specifications of volumes are as follows.
|
Item |
Specifications |
|---|---|
|
Maximum number of simultaneous operations of volume operations and snapshot operations |
Approx. 20 If you perform 20 or more operations at the same time, operations might not be performed successfully due to a timeout. Volume operations see volume creation, deletion, expansion, and setting edition. Snapshot operations see preparation for, taking, deleting, and restoring snapshots. A single operation handling multiple volumes is counted as one operation. For example, a volume creation operation with 20 or more volumes specified is counted as one operation. Completion of the job means completion of the operation. When the job state is "Succeeded", the operation is complete. |
|
Volume name |
Number of characters: 1 to 32 Characters that can be used: Numbers (0 to 9), uppercase alphabet (A to Z), lowercase alphabet (a to z), symbols (- , . : @ _) |
|
Volume nickname |
Number of characters: 1 to 32 Characters that can be used: Numbers (0 to 9), uppercase alphabet (A to Z), lowercase alphabet (a to z), symbols (- , . : @ _) |
About the Quality of Service (QoS) function
QoS setting can be applied to volumes. The QoS function provides various performance levels (such as I/O or the amount of transfer) for each volume. When a storage system is shared by multiple services or when multi-tenancy configuration in which multiple companies (services) coexist is applied in the public cloud, required storage performance levels differ depending on services (applications). In normal storage settings, requests for excessive I/O operations from an application have a tendency to degrade the performance level of other applications because an attempt to perform I/O processing is made in the order of requesting. In such a case, using the QoS function that enables controlling I/O processing in units of volumes can suppress performance interference between applications and provide a certain level of performance and quality.
In detail, the QoS function provides the following:
-
Function for controlling the performance upper limit for host I/Os for specific volumes
-
Function for monitoring alert threshold values of volumes subject to QoS
VPS administrators can set upper limit performance values for individual volumes on the condition that set values do not exceed the upper limit performance values of volumes in a VPS. QoS alert settings cannot be made.
Controlling the upper limit by using QoS
The function for controlling the upper limit provided by QoS determines the performance upper limit when a storage system performs I/O processing for the services that requested the I/O.
Each volume has its upper limit value. Read and write processing is not differentiated. Therefore, their respective upper limits cannot be separately set. When I/O processing is requested for a volume with the upper limit set, a storage system verifies the average number of I/Os and the average amount of transfer for the volume in the last one second. After the I/O upper limit is reached, the subsequent processing will be suppressed although I/O requests from services are accepted. When the number of I/Os or the amount of transfer (or both of them) become lower than the upper limit, I/O processing is resumed. The QoS function provides methods for controlling the upper limit by the number of I/Os (upperLimitForIops[IOPS]), by the amount of transfer (upperLimitForTransferRate[MiB/sec]), or by both of them. For the method of controlling the upper limit by both the number of I/Os and the amount of transfer, I/O processing is suppressed when either of them reaches the upper limit.
The QoS function controls the upper limit based on the average number of I/Os or the average amount of transfer per second. However, performance information that can be referenced is collected at five second intervals even for high-resolution information. Therefore, in some cases, control of the upper limit by QoS cannot be observed.
The performance information about a storage system includes I/O processing that occurs within the system due to capacity balancing or volume migration that is performed when a storage node is removed. However, this I/O processing that occurs within the system is excluded from the target of the QoS function. As a result, when you reference the performance information about a storage system, for each volume, the number of I/Os might exceed the QoS upper limit by approximately 80 [IOPS] and the amount of transfer might exceed the QoS upper limit by approximately 20 [MiB/sec].
The following shows the range of upper limit values that can be set for QoS. When creating volumes, QoS settings of volumes set for a VPS are automatically set if you omit specification of the QoS settings. You can set upper limit performance values for individual volumes on the condition that set values do not exceed the upper limit performance values for volumes in a VPS.
| Item | Number of I/Os [IOPS] |
Amount of transfer [MiB/sec] |
|---|---|---|
|
Range of upper limit values that can be set |
-1 (upper limit is not set), 100 to 2,147,483,647 |
-1 (upper limit is not set), 1 to 2,097,151 |
Data reduction function of volumes
The VPS administrator cannot configure the data reduction function for volumes.