Home > Articles

Block Storage Cloud

Elizabeth Joseph introduces the concept of block storage and provides example usage. The basics of OpenStack Cinder block storage architecture are explained, and then you are walked through configuration. You then attach a Cinder block storage device to a compute instance, partition it, give it a file system and mount it inside your compute instance so you can add files to it.

This chapter is from the book
  • The road to the City of Emeralds is paved with yellow brick.
    L. Frank Baum, The Wonderful Wizard of Oz

OpenStack provides two popular mechanisms for storage: object and block storage. Block storage is traditionally what you’d mount as a file system on your server. Object storage instead hosts individual files that are then referenced from within your application. In Chapter 9, “Object Storage Cloud,” you learn about why you may want to use object storage with Swift to host files. This chapter covers block storage with Cinder.

Integrated with the rest of OpenStack, Cinder volumes can be created within an OpenStack cloud and then live mounted to a specified instance at the whim of a user. Additionally, you can unmount that volume from one instance and mount it on another with just a few commands.


One of the strengths of OpenStack is to avoid vendor-lock in, particularly when used in combination with versatile solutions like Cinder. Cinder provides an abstraction layer through the volume manager that hooks in to over 70 different proprietary and open source storage solutions. Additionally, it can be an interface to multiple back ends at once, enabling you to not only diversify your back ends across vendors but also change them out and do a planned migration as your organization sees fit.

Cloud Provider

Whether you’re running a public cloud accessible to customers or a private cloud for use within your organization, offering the capability to extend the given file system requirements in place for the flavors can be a huge benefit.

With the capability to add block storage volumes on the fly, the storage requirements for default compute nodes can be kept small to preserve space for users who want to focus on compute power and give others the flexibility to add the storage they need on the fly. The flexibility to extend storage as needed helps scaling out resources without over-committing beforehand and makes migrations easier if data is kept on a single volume that can be moved to a new compute instance.

Another major benefit is that the compute nodes can be run on throw-away commodity hardware. The data needing to be stored can be either kept on expensive redundant enterprise hardware or on something that has built-in redundancy like Swift. As a result, compute nodes themselves could become independent, throw-away components of your infrastructure, spun up as needed and replaced with identical servers that attach to your storage back ends. Finally, upgrades are also simplified for your customers. If you have a new copy of your system you are testing, you can snapshot the production data from a Cinder volume and then attach it to your test system to see if it works.

Data Processing

Whether you’re a film production company or a research institution, using compute nodes to do data processing and analysis is a common use for cloud-based infrastructures. But where is this data stored and how is it shared in your organization? What do you do when the compute nodes you’re working on run out of space? With Cinder block storage users are able to extend volumes after creation or simply create new volumes as they are needed and attach them to their running instances and mount them in a matter of minutes. Running out of hard drive space on an instance because you have too much data is no longer a problem.

Additionally, if you realize you need more processors or memory, it’s simple to create a new compute instance and move the volume over to the new instance. All your data moves with you to your new server.

Keeping Backups

Making sure your data is backed up and replicated is a common concern, and Cinder offers several options for this. As mentioned earlier, it provides an abstraction layer for dozens of back ends, so you have a lot of options in your environment and on top of that, the different types of backups that Cinder offers.

Many virtualization technologies supported by OpenStack have built in snapshot capabilities, but OpenStack’s block storage also has one. This enables volumes to be backed up as snapshots to other block storage volumes and can be used on its own, using the existing configuration. Whether offered as a backup service by a cloud provider or as an automatic service for users on an OpenStack cloud, this is a valuable service.

You can also clone volumes. Many back ends are smart enough to do a copy-on-write in where zero copying actually happens. The new volume references an existing volume it was cloned from and writes data on top of that. This makes it very fast. Some snapshot features also just do this in the backend, but every vendor solution is implemented differently.

Moving beyond snapshots, Cinder also offers a backup service that enables you to back up your block data to an object store. This helps with the scenario of your entire block storage backend going completely off-line. This backup service more efficient. Differential and incremental backups can be performed and, unlike a snapshot, it is only backing up data that was actually used, not the entire volume and unused bits.

We won’t spend a lot of time on backup scenarios in this chapter. Instead we’ll be focusing on adding volumes in a more instance-focused environment where you’re adding volumes to instances, but they are great options to keep in mind.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020