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

Description

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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.

Introduction to Cloud Server Local Storage

CloudControl currently supports local storage via storage volumes (i.e. "disks") that are attached to a variety of virtual controllers which emulate a specific hardware type. Most Images and Servers use SCSI controllers for this purpose, but effective with the June 2017 release, the system now supports IDE and SATA controllers as well as read-only files on CD-ROM and Floppy devices. 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. ISO and FLP files do not have disk speeds and are always on the Standard disk speed.

From the Operating System, each local disk appears to be an external hard disk attached to a specific spot on the controller. When a Cloud Server is deployed, it will inherit the same virtual controllers, 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

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

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 on 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 on 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

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.

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

Virtual SATA Controllers

The system supports up to four virtual SATA controllers per Cloud Server. All SATA controllers emulate a standard AHCI 1.0 Serial ATA Controller (Broadcom HT 1000) - there are no separate adapters as there are with SCSI controllers. As described in VMware SCSI Controller Options, use of SATA controllers is not recommended for high I/O environments.

Each SATA controller provides 30 "positions" in which either a local storage "disk" or a CD-ROM device can be attached. These positions are numbered from 0 through 29. This means that with the full compliment of four SATA controllers, there are 120 potential positions where either local disks or CD-ROM devices can be placed.

SATA controllers are supported only if already present on Images or Servers, you cannot add or remove SATA controllers on an existing Cloud Server. Therefore, if you wish to use SATA, you will need to import a Client Image with the desired number of SATA controllers already present. SATA is not supported on all Operating Systems. Check the VMware Compatibility Guide for more details.

Virtual IDE Controllers

The system supports up to two virtual IDE controllers per Cloud Server. All IDE controllers emulate a standard Intel 82371AB/EB PCI Bus Master IDE controller - there are no separate adapters as there are with SCSI controllers.

Each IDE controller provides only two "positions" in which either a local storage "disk" or a CD-ROM device can be attached - slots 0 and 1. IDE works under a Master/Slave configuration, so the "1" position can be used only if either a "disk" or CD-ROM device is in the "0" position of the same controller. Therefore, the system will prevent deletion of a local disk in position 0 if there is a local disk in position 1.

VMware's import process inserts IDE controllers on all images imported through the OVF process, so the controllers are present on almost all Images and Cloud Servers. The system does not support addition or removal of IDE controllers.

NOTE: IDE Controllers do not support "expanding" a disk and require the server to be powered off in order to add a disk to the controller.

CD-ROM Devices

CD-ROM devices may be present on IDE or SATA controllers only if already present on Images or Servers, you cannot add or remove the CD-ROM devices from the controller. Therefore, if you are looking to use a CD-ROM device as described below, you will need to import a Client Image with the desired CD-ROM devices and/or ISO files already present.

CD-ROM devices may have an ISO file attached, in which case they provide read-only access to the ISO file through the virtual CD-ROM device. Otherwise, the CD-ROM device does not provide any use. All such ISO files are placed on Standard Disk Speed (see below for details) and billed based on their file size as if they were a local disk on Standard disk speed. A server or image can have as many CD-ROM devices and ISO files as supported by the controllers, but the total combined size of all ISO and FLP (see below) on a Cloud Server/Image cannot exceed the Maximum Disk Size (GB) for the data center location.

Currently, the system allows ISO only if it is already present on the Image or Server, so they need to be included on an Imported Image. ISO files may be permanently removed from a Cloud Server, but they cannot be added, modified, or replaced. You will have to import a new Image if you want to make changes. 

Floppy Controllers

The system does support up to two Floppy Controllers that can have a FLP file attached, in which case they provide read-only access to the FLP file through the virtual floppy device in the same manner as ISO support. The system allows Floppy and associated FLP files only if it already present on the Image or Server, so they need to be included on an Imported Image. FLP files may be permanently removed from a Cloud Server, but they cannot be added, modified, or replaced. You will have to import a new Image if you want to make changes.

Disk Minimums and Maximums 

Beyond that, there are four sets of limits associated with local storage on a Cloud Server, each of which varies 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 are set as follows in most Public Cloud locations. However, as noted above, these values may vary in other locations:

PropertyMCP 2.0 Public SettingMCP 1.0 Public Setting
Maximum Total Storage for Cloud Server (GB)30,00011,000
Maximum Total Storage for Client Image (GB)3,0002,600
Minimum Disk Size (GB)110
Maximum Disk Size (GB)10001000
Minimum Disk Count11
Maximum Disk Count6015

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 controller and position on which to install the drive or have the system insert the drive in the "next available" SCSI 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:

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.

IOPS/GB Threshold Not Currently Implemented in Public Cloud Locations

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The IOPS/GB thresholds described in this section represent planned thresholds for each disk speed in Public Cloud locations. However, these thresholds are not currently enforced by the system but may be enforced at any time in the future. Users should plan their usage of disk speeds in Public Cloud around these expectations

Each "disk speed" has an 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 associated Controller with the position 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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