Cloud Files - FAQs

Getting Started

How can I get live support for Cloud Files?

Support is available by email at Monday through Friday, 9AM to 5PM CST. Tech support will be happy to answer any questions you have about Cloud Files, except for code related issues. If you do have questions about design or coding please try our forums or documentation.

What is a container in Cloud Files?

A container is a “storage compartment” for your data and provides a way for you to organize that data. You can think of a Container as analogous to a folder in Windows® or a directory in UNIX®. The primary difference between a container and these other “file system” constructs is that containers cannot be nested. You can have up to 500,000 Containers in your account, but they only exist at the “top level” of your account and containers cannot reside within other containers.

Containers scale to about one million objects before performance degrades. Containers can only be removed from Cloud Files if they do NOT contain any storage Objects. In other words, make sure the container is empty before attempting to delete it.

What are the naming requirements for Cloud Files objects and containers?

The naming requirements for Cloud Files objects and containers (such as illegal characters and name length limits) include:

  • Container names may not exceed 256 bytes and cannot contain a slash (/) character.
  • Object names may not exceed 1024 bytes, but they have no character restrictions.
  • Object and container names must be URL-encoded and UTF-8 encoded.

How do I access Cloud Files?

First you must make sure you have generated a valid API Access Key. Then you can use either the Cloud Files user interface in the Rackspace Cloud Control Panel or one of our programming interfaces.

See Cloud Files and CDN for more details.

What does eventual consistency mean in Cloud Files?

A key characteristic of Cloud Files is eventual consistency. In computing, the CAP (Consistency, Availability, and Partition Tolerance) theorem states that distributed systems cannot achieve consistency, availability, and network failure tolerance; they can achieve only two. For example, a system can be consistent (that is, all reads get the most current data) and handle network failures, but must sacrifice availability to do so. Or, a system can choose to handle network failures and have perfect availability, but must sacrifice consistency to do so. Distributed systems must always handle network failures, so they must choose to sacrifice either availability or consistency.

Storage systems become distributed as they grow. OpenStack Swift (the basis for the Rackspace Cloud Files service) sacrifices consistency for availability and network failure tolerance. This choice enables the system to scale to enormous levels and to provide massive uptime, but it also means that in certain scenarios some data might not be updated throughout the entire system. For example, a container listing might not be updated immediately after an object is written. OpenStack Swift queues the container listing update and allows the object write to succeed. This sort of consistency model is called eventual consistency.

Where can I find Cloud Files documentation?

Account Services

Can Cloud Files be used for my Cross-domain policy file?

No. The Cloud Files CDN does not support exposing a custom crossdomain.xml file, as this is a required file by the OpenStack Swift project. OpenStack Swift uses this as a global configuration file for the installation, and can not be modified for multiple tenants, such as our Public Cloud.

Is there a Cloud Files specific SLA?

Please click here to view The Rackspace Cloud Terms of Service.


Why does uploading a file in the Cloud Control Panel set the Allow-Origin header on my container?

When you upload a file in the Cloud Control Panel, an Allow-Origin header is set on the container to support cross-origin resource sharing (CORS). Browsers prevent AJAX requests between different domains by default. Because the Cloud Files API and the Cloud Control Panel reside on different domains, CORS must be enabled to support uploads directly to a container. When the upload succeeds, the CORS headers are removed.

By allowing the browser to upload directly to the Cloud Files API, maximum upload performance can be achieved.

Read more about CORS at .

How do permissions work?

There are no permissions or access controls around containers or objects other than being split into separate accounts. Users must authenticate with a valid user name and API Access Key, but once authenticated, they can create or delete containers and objects only within that account.

At this time, there is no way to publicly access the objects stored in Cloud Files unless that container is published to CDN. Each request to Cloud Files must include a valid “storage token” in an HTTP header transmitted over a HTTPS connection.

Cloud Files Streaming

Why have we chosen to support specific players?

Many Rackspace customers are not flash developers, but still want to use a streaming offer. There are a few players that are dominating the market, and we will plan to support each of them. Custom plugins are required in order for Streaming delivery to work properly over the Akamai network. As Akamai adds support for more players, our customers will have access to them.

Why are we not using RTMP?

RTMP is probably the most popular delivery format today, but the market is quickly moving towards HTTP delivery for Streaming content. Following are just a few reasons the market is moving towards HTTP:

  • Accessibility - Many firewalls block RTMP and RTSP streaming protocols because corporations don’t want users watching video at work. HTTP appears to be normal web traffic, meaning that videos served over HTTP are usually left open.
  • Startup times - Akamai sees a significant reduction in stream startup times on average for traffic served via HTTP.
  • Throughput (image quality) - With the HTTP network being larger than many other networks, Akamai is closer to the end user on their HTTP network meaning they get better throughput of data. that means customers will experience higher bit rates uninterrupted (and without buffering) and increase the end user’s over all experience.

Is this available internationally?

Yes, this is available to both US and UK Cloud customers.

Content Delivery Network

Does CDN management in Cloud Files support exposing a custom crossdomain.xml file?

Cloud Files CDN does not support exposing a custom crossdomain.xml file because this file is required by the OpenStack Swift project, on which Cloud Files is based.

OpenStack Swift uses the crossdomain.xml file as a global configuration file for installation. The file cannot be modified for multiple tenants, such as our Rackspace Public Cloud.

For more information, see Cross-domain Policy File.

If your site requires a custom crossdomain.xml file, we suggest you take a look at Rackspace CDN. Rackspace CDN allows you to customize your configuration and define your own origin web server.

What is the TTL attribute in a Cloud Files container?

When you create a container in Cloud Files and you make that container public, the files within that container have a designated TTL. The TTL is the time interval after which the CDN will reread the contents of the container. For more information on how to mange the TTL attribute, see Manage Time to Live (TTL) in a Cloud Files Container.

What is the CDN?

Using the Akamai content delivery network (CDN) service, Cloud Files brings you a powerful and easy way to publish content over a world-class industry leading CDN. For more information on how to use CDN with Cloud Files, see Getting Started with Cloud Files and CDN.

Who is Akamai?

Akamai Technologies, Inc. is publicly traded: (NASDAQ: AKAM) company founded in 1998. Akamai has a pervasive, highly-distributed cloud optimization platform with over 73,000 servers in 70 countries within nearly 1,000 networks.

What will I experience when Akamai is implemented as my new CDN provider?

Rackspace expects no customer impact during your transition to Akamai. Once we flip the switch to have a customer’s content served by Akamai, Akamai will begin supporting both new URLs and all other existing CDN provider URLs.

This means that CDN customers who currently have Limelight URLs coded into their websites will continue to serve content using those URLs when they are transitioned to Akamai, but they will be distributed over the Akamai network. At this time, we do not have any plans to discontinue the legacy URLs.

If a customer requests their URL (either in the Cloud Control Panel or through API) for an object, they will be presented with a new Akamai URL. This does not mean that old URLs are invalid. However, as Rackspace releases new features like CNAME and SSL, customers will need to reference their new Akamai URL instead of their legacy URL.

Will customers have to change their code to use Akamai?


Will customers have to do anything different in the Cloud Control Panel?

No, as we add new features, we will educate our customers.

Should customers anticipate any downtime during this implementation?

No downtime is expected during the implementation of the Akamai platform.

Will the Cloud Files API be different?

No, all customers facing API calls will remain the same.

What are the benefits Of using a CDN?

  • Higher capacity and scale- Strategically placed servers increase the network backbone capacity and number of concurrent users handled. For instance, when there is a 10 Mb/s network backbone and 100 Mb/s central server capacity, only 10 Mb/s can be delivered. But when 10 servers are moved to 10 edge locations, total capacity can be 10*10 Mb/s.
  • Lower delivery costs - Strategically placed edge servers decrease the load on interconnects, public peers, private peers and backbones, freeing up capacity and lowering delivery costs. A CDN offloads traffic on a backbone network by redirecting traffic to edge servers.
  • Lower network latency and packet loss - End users experience less jitter and improved stream quality. CDN users can therefore deliver high definition content with high Quality of Service, low costs and low network load.
  • Higher Availability - CDNs dynamically distribute assets to strategically placed core, fallback and edge servers. CDNs may have automatic server availability sensing with instant user redirection. CDNs can thus offer 100% availability, even with large power, network or hardware outages.
  • Better Usage analytics - CDNs can give more control of asset delivery and network load. They can optimize capacity per customer, provide views of real-time load and statistics, reveal which assets are popular, show active regions and report exact viewing details to customers.

File Transfers and File Sharing

Does Cloud Files support the transfer of large files?

Yes, the Rackspace Cloud now supports the transfer and storage of larger files. Following is a list of frequently asked questions about our large file support.

How does Rackspace support the upload of large files to Cloud Files?

Although support for uploading content to Cloud Files through the Cloud Control Panel is limited to files smaller than 5 GB, we can accommodate the transfer of files larger than 5 GB by allowing you to segment your files into multiple file segments.

How large should my file segments be?

Rackspace does not enforce any lower limits on the file size. File segments cannot be larger than 5 GB, and we recommend not storing file segments that are smaller than 100 MB.

Can I serve my large files over the CDN?

At this time, you cannot serve files larger than 10 GB from the CDN.

Is there a simpler way to use this process?

We have created a tool called Swift to make this process easier. Swift segments your large file for you, creates a manifest file, and uploads the segments accordingly. After it uploads the segments, Swift manages the segments for you, deleting and updating them as needed. You can get information about the Swift Tool and download the Swift tool.

When should I use the API instead of the Swift tool?

If you are interested in developing against the Rackspace Large File Support code to incorporate into your application, you should work directly with the Cloud Files API. For more information, see Use the API to manage large files.

When should I use the Swift tool instead of the API, and what is the process?

If you want to upload large files but do not want to incorporate our code into an application, you might find it easier to use the Swift tool for your uploads and management. For more information, see Use Swift to manage large files.

What will the download experience be like?

After files are segmented and uploaded with a manifest file, your large file will be served as a single file, so the experience will mimic the download or service of any other object retrieval.

Do I have access to my file segments?

Yes, you can edit your file segments just like any other object within Cloud Files.

How do I ensure that my files are linked correctly?

Include your manifest file in your upload. You can change your file name by editing this manifest file as well. We recommend using prefixing in your file segments to easily map your manifest file to the portions of your large file. For example, you could name your segments as follows:


In this case, you would point your manifest file to the prefix: Myfavoritemovie .

Can I use this feature from the Cloud Control Panel?

At this time, Rackspace has not implemented this functionality into the Rackspace Cloud Control Panel.

Application Development

Where can I find Cloud File Developer Guides?

Developer guides are available on the Rackspace API documentation site. Documentation is available for the raw API and for language-specific SDKs.

Why does one of my Cloud Files scheduled tasks get terminated abruptly?

The Rackspace Cloud system restricts the maximum execution time of any one cron job to 15 minutes. Please make sure that your script is well tested and can complete its intended job within this time frame.