Introduction to Cloud Server Local Storage and Disk Speeds (Tiered Storage)

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Provides an overview of both local Cloud Server Disks and Tiered Storage, which provides different levels of disk performance for local Cloud Disks.

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Introduction to Cloud Server Local Storage

CloudControl currently supports local storage via storage volumes (i.e. "disks") that are attached to a virtual SCSI controller. Being a virtualized environment, each storage volume ("disk") is delivered via a VMDK file that's deployed to a LUN on the underlying Cloud SAN infrastructure. Each disk is assigned a "disk speed" which determines the performance characteristics of the underlying storage that will be used for that specific local storage volume. Local disks using the same disk speed may or may not be deployed to different physical LUN's on the SAN infrastructure.

From the Operating System, each local disk appears to be an external SCSI disk attached to a specific spot on the SCSI bus. When a Cloud Server is deployed, it will inherit the same virtual SCSI controllers, SCSI disk sizes, and disk locations as the Source Image. However, users can choose to modify the speed of a disk on a deployed Server to be different than that which was used when the Image was created. For details, see the instructions on how to deploy Servers at How to Deploy a Cloud Server from a Guest OS Customization Image and How to Deploy a Cloud Server from a Non-Guest OS Customization Image. Since the system "defaults" to the disk speed of the Source Image, users can also modify the default disk speeds associated with a Client Image as described in How to Manage a Client Image.

Note: Client Images always use Standard Storage and are always billed as Standard Storage. Client Images do have “disk speeds", which are metadata that the system defaults to when you deploy a server from that Image.

Virtual SCSI Controllers and Adapters

The system supports up to four virtual SCSI controllers per Cloud Server. Each SCSI controller uses a specific "adapter" that defines how the SCSI controller is perceived by the guest Operating System. There are four adapters supported by vSphere:

  • BusLogic Parallel - This was one of the first two emulated vSCSI controllers made available in the VMware platform, and remains commonly used on older versions of Windows as the driver is available by default.
  • LSI Logic ParallelThis was the other emulated vSCSI controller made available in the VMware platform and remains commonly used on UNIX Operating Systems 
  • LSI Logic SAS - This is a newer evolution of the parallel driver supported (and in some cases required) for newer versions of Microsoft Windows. It was designed to replace the BusLogic Parallel adapter and provides better performance than the original BusLogic Parallel adapter.
  • VMware Paravirtual - This is a VMware-specific driver that is virtualization-aware and designed to support very high throughput with minimal processing cost and is, therefore, the most efficient driver. However, this driver requires that VM Tools be installed and running in order to function properly. There are some other restrictions, particularly on older operating systems - review the appropriate VMware documentation for more details. 
  • More details on each of the adapters described above are available the VMware Blog article Which vSCSI controller should I choose for performance?

Note that although there are four adapters supported, VMware does not support all of them on every Operating System. When adding a Controller, the system will only make available adapters approved for the Server's Operating System. The Supported Operating Systems dashboard will help you identify what adapters are "available" and which one is "recommended" by VMware for a given operating system as described in Navigating the Supported Operating Systems Dashboard

Users can add or remove SCSI controllers for a Cloud Server as described in:

Disk Positions, Sizes and Quantities

Each SCSI controller provides 15 "positions" in which a local storage "disk" can be attached. These positions are numbered from 0 through 15, with the 7 position reserved as it is used by the virtual SCSI adapter. This means that with the full compliment of four SCSI controllers, there are 60 potential positions where local disks can be placed.

Most Server BIOS are programmed to boot the Operating System from SCSI Controller 0, Position 0, but users can modify the BIOS through the Console to change this behavior. 

Beyond that, there are four sets of limits associated with local storage on a Cloud Server, each of which vary by User-Manageable Cluster or Data Center location and can be identified as described in How do I Identify Hardware Specifications and Capabilities Available in a Data Center Location:

  1. The size of each individual disk must fall within a specified range of Minimum Disk Size and Maximum Disk Size
  2. The total number of disks must fall within the range dictated by the data center location's Minimum Disk Count and Maximum Disk Count
  3. Maximum Total Storage defines the maximum aggregate amount of "local" storage associated with a Cloud Server
  4. There is a smaller Maximum Total Storage for an Image limit on the total size of the Cloud Server if it can be cloned to create a Client Image.

Effective March 23, 2017,  the limits will be set as follows in Public CaaS locations – but as noted above, these values may vary in other locations:

Property

MCP 2.0

MCP 1.0

Maximum Total Storage for Cloud Server (GB)

30,000 (was 14000)

11,000

Maximum Total Storage for Customer Image (GB)

3,000 (was 2600)

2,600

Minimum Disk Size (GB)

1 (was 10)

10

Maximum Disk Size (GB)

1000

1000

Minimum Disk Count

1

1

Maximum Disk Count

60 (was 14)

15 (was 14)

 

When disks are added to a Cloud Server, they will appear as unformatted drives that need to be formatted for use. A User can choose a specific SCSI position on which to install the drive or have the system insert the drive in the "next available" position. For additional details on how to add a disk, see:

These disks can also be removed from the Cloud Server as described in:

Any individual disk attached to a deployed Cloud Server can be increased in size should greater capacity be required – though note that like a newly-added disk, the additional storage is delivered as an unformatted increase in the size of the volume and therefore needs to be formatted by the OS for use. For more details, see:

Other Types of Storage Controllers

vSphere supports local volumes ("disks") on both IDE and SATA controllers. These controllers are not currently supported by CloudControl and the system will prevent the import of Images if such controllers are present. Support for these controllers is scheduled to be added in an upcoming release in mid-2017.

Historically, the system did have a bug that would allow Images to be imported with the IDE/SATA disks incorrectly identified as SCSI. Most disk-management functions did not work with such disks, but they were able to deploy successfully. As part of adding support for multiple SCSI controllers, the CloudControl release on March 23, 2017 is reconciling its record of CloudControl disk storage to match what is currently deployed in vSphere. If there are any Cloud Servers with non-SCSI disks, those disks may no longer be reflected in CloudControl (i.e. from a CloudControl perspective, they will "disappear" from the UI/API). Be assured there is no change to the local storage itself – any such disk will remain attached and working on the Cloud Server. It will just no longer be reflected in CloudControl. It will be re-discovered and presented in the UI/API again when support for IDE/SATA is added in the upcoming release.

Introduction to Disk Speeds (Tiered Storage)

Local storage has a specific "disk speed" that defines the performance characteristics associated with the local storage. If the SAN infrastructure in a given Data Center offers different types of performance characteristics, the CloudControl software will allow you to decide which performance characteristic a given Cloud Server disk should utilize. Disk speeds allow the user to select a level of performance that is focused on the intended function of the disk. For example, log file storage might require a lower level of performance while database files may require a faster level of performance. Because the disk speed can be set at an individual disk level, a given Cloud Server can have different disk speeds depending on how they plan to use the disks.

Each "disk speed" has a IOPS/GB threshold that defines the maximum possible performance. This threshold merely defines the ceiling on IO performance - it is not a guarantee of actual performance that may be available at a given time. Since the threshold is "per GB", it operates based on the size of the disk - a 1,000 GB disk will get more total IOPS than a 100 GB disk. For example, Standard disk has a 1.00 IOPS/GB threshold. So a 100 GB disk has a maximum performance threshold of 100 IOPS while a 500 GB disk has a maximum performance threshold of 500 IOPS.

Each local storage volume is treated independently in terms of its threshold and performance. To increase IOPS performance for a given volume, users can either increase the size of the volume or (where available) upgrade to a higher-performing disk speed.

defines the ceiling on IO performance. Achieved performance is determined by real-time contention for resources, i.e. no “IOPS reservation” exists

In Public Cloud environments, the specific performance characteristics of each disk speed are:

  • Standard - Standard disk is the "default" level of storage and matches the level of performance available prior to the introduction of disk speeds. It is available in all Data Centers. Cloud disks deployed as Standard speed are deployed on LUN's powered by a Hybrid Disk configuration consisting of 2 TB 7200 RPM Nearline SAS disks in a RAID5 configuration that is fronted by an extensive "Fast Cache" Solid-State Disk infrastructure. The maximum IOPS threshold for this disk speed is 1.00 IOPS/GB.
  • High Performance - High Performance disk provides faster I/O performance than the Standard speed. Cloud disks deployed as High Performance speed are deployed on LUN's powered by a Hybrid Disk configuration consisting of 600 GB 15000 RPM Nearline SAS disks in a RAID5 configuration that is fronted by an extensive "Fast Cache" Solid-State Disk infrastructure. The maximum IOPS threshold for this speed is 2.50 IOPS/GB.
  • Economy - Economy disk provides slower I/O performance than the Standard speed. Cloud disks deployed as Economy speed are deployed on LUN's powered by a disk configuration consisting of 3 TB 7200 RPM Nearline SAS disks in a RAID5 configuration. There is NO "Fast Cache" fronting for this storage level. The maximum IOPS threshold for this speed is 0.30 IOPS/GB.

Standard "disk speed" is tracked based on "Storage Hours" pricing element. The other speeds are tracked based on "High Performance Storage Hours" and "Economy Storage Hours". In Public Cloud environments, each disk speed carries a different hourly pricing. 

The "disk speed" associated with each Server is visible in the Manage Server dialog of the Admin UI in a row that is shown underneath the SCSI Controller with the SCSI ID and size of the individual disk:

Availability and Use of Different Disk Speeds

The availability of specific Disk Speeds is configured for each Data Center and User-Manageable Cluster. (User-Manageable Clusters are available in certain Private Cloud and Hosted Private Cloud Data Center locations. For more information about User-Manageable Clusters, see Introduction to User-Manageable Clusters.) As such, not all User-Manageable Clusters and Data Center locations have the same "disk speed" infrastructure available. Only the "Standard" disk speed is available in all Clusters and Data Centers. To identify what speeds are available in a given Cluster or Data Center, view the summary information as described in How do I Identify Hardware Specifications and Capabilities Available in a Data Center Location

It is possible, although unusual, for a disk speed to exist, but not currently be available for use on new disks added to a Server. You can identify this condition (and the reason why it's no longer available) through the "Disk Speeds Available" field when viewing a Data Center's capabilities as described in How do I Identify Hardware Specifications and Capabilities Available in a Data Center Location.

How to Use Multiple Disk Speeds

There are two ways to set the disk speed for a Cloud Server:

  • You can choose the specific speed of each disk when a Server is deployed. By default, the Admin UI will present the "default" disk speeds associated with an OS or Client Image. You can modify these "default" speeds through a dialog on the Server as described in:
  • Client Images inherit the "default speed" of each disk based on the speed of the disks on the Cloud Server when the Image was created. You can edit the "default speed" of each disk associated with a Client Image as described in:
    • How to Manage a Client Image
    • Note the Client Images lose any disk speed characteristics when a Client Image is exported, as the OVF format does not support disk speed information. This means that all Imported Images will initially have all disk speeds set to Standard.
  • Once a Server is deployed, you can change the disk speed of an individual disk as described in:

As always, these functions are also available programmatically as described in the API documentation. 

Reporting and Billing for Different Disk Speeds 

Each different "disk speed" will be charged at its own rate, reflecting the relative performance level. Refer to your Cloud product pricing page for more information.

From a reporting perspective, the system will now provide separate reporting for each disk speed that's available within a Geographic Region. This impacts the reports as follows:

  • The Summary Usage Report:
    • The Storage Hours column tracks the usage of Standard disk speed.
    • An additional column is added for each additional disk speed available in a given Geographic Region.
    • See How to Create a Summary Usage Report
  • The Detailed Usage Report:
    • The Storage Hours column tracks the usage of Standard disk speed.
    • An additional column is added for each additional disk speed available in a given Geographic Region.
    • See How to Create a Detailed Usage Report
    • Columns will be present for each disk speed available in any Data Center location in a Geographic Region, for all accounts in the Geographic Region. This reporting will appear regardless of whether any of the account's Servers are actually using these speeds or whether the account even has access to a Data Center location supporting the disk speed.

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