Last updated on: 2017-05-04
Authored by: Rackspace Support
This article describes some of the major features and benefits of the General Purpose and work-optimized flavors of Cloud Servers compared to the Standard server class. General Purpose and work-optimized servers have been updated to align with industry standards, improve server imaging, and consistently allocate adequate disk resources for each server.
I/O-optimized servers are assigned networking resources and use local high-speed SSD drives for storage. I/O-optimized servers work best for applications that require frequent or sustained disk access, like databases.
Compute-optimized servers have a high CPU allocation to optimize the server for applications with high CPU demands, like web servers and application servers. All disk storage for Compute-optimized servers is on Cloud Block Storage.
Memory-optimized servers have larger allocations of low-latency RAM for memory-intensive applications like caching servers, in-memory analytics, and search indexes. All disk storage for Memory-optimized servers is on Cloud Block Storage.
General Purpose and I/O flavors use faster solid state drives (SSD). I/O flavors also have secondary data disks, which are not captured during an imaging operation. For more information about data disk imaging limitations, see the article Create an image of a server and restore a server from a saved image.
You can back up the data on your data disk or disks by leveraging either Rackspace Cloud Backup or Rackspace Cloud Block Storage which can used to increase the storage capacity of your server, if needed. For a comparison of the two data disk backup options, see Best Practices for Backing Up Your Data: Cloud Block Storage versus Cloud Backup.
The following features noticeably reduce the time to provision General Purpose and work-optimized servers:
General purpose and work-optimized flavors feature a maximum of 240 GB RAM per server, as compated to only 30 GB in the Standard server class.
General Purpose and work-optimized flavors provide more processing power: up to 32 vCPUs or virtual cores, compared to a maximum 8 vCPUs on the largest-size server in the Standard server class. For information, see Work-optimized server types.
General Purpose and work-optimized servers provide more network bandwidth: 40 GigE to each host server, the physical machine that houses your virtual server. Each host server gets 20 GigE for management and Cloud Block Storage, and 20 GigE for the server’s public network, ServiceNet, and network traffic. This bandwidth dramatically improves the interoperability of servers with complementary services such as Cloud Block Storage over the Standard server class.
Separating the operating system from the data provides higher maximum input/output operations per second (IOPS). For example, a 1 GB General Purpose server with 20 GB of system disk and no data disk can process about 20k IOPS. A 120 GB I/O-optimized server with a 40 GB system disk and 1200 (or 4x300) GB data disks can perform about 80k IOPS. Compare this with the Standard server class for Cloud Servers, which can process approximately only 2k IOPS.
Standard servers can resize up or down, but General Purpose servers can resize only up, and work-optimized servers cannot dynamically resize at all.
Along with the rest of the OpenStack community, Rackspace is reducing support for this feature because it does not align with the industry-standard method of scaling. Rather than resize one server for vertical scaling, we instead recommend employing horizontal scaling, adding or removing the number of servers managed by a load balancer to manage your available resources to suit your needs.
For information about reducing the size of your General Purpose server or changing the size of your work-optimized server, see Upgrading resources for General Purpose or I/O optimized Cloud Servers.
Because I/O-optimized servers have a separate system disk and data disk, you must prepare your data disk by formatting and mounting it to your server before you can use it. Follow the instructions in these articles to prepare your data disk for use:
The 512 MB RAM cloud server is not available for General Purpose and work-optimized flavors. For a server that uses shared CPU and networking resources, maintaining the bursting capabilites of the 512 MB size places too much stress on the host, and could potentially negatively impact other servers on the host computer.
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