Object storage stores data in a flat address space. Data is stored and retrieved using RESTful API calls over HTTP. This in contrast with regular file systems, that store data in hierarchical, directory-based file systems that utilize specialized storage protocols.
Where a traditional file system provides a structure that simplifies locating files (for example, a log file is stored in /var/log/proxy/proxy.log), in object storage, a file’s location must be administered by the application using the object ID. For example, an application has administered that its log file has an object ID of 8932189023.
An object storage container stores the actual data (for example, a document, an image, or a video file), its metadata (for example, date, and size), and a unique Object ID. Amazon’s S3 service pioneered object storage and its protocol became the de facto standard protocol for object storage.
The flat address space in an object storage system enables simplicity and massive scalability of the storage system, as the Object ID is a link to a physical file that can be stored anywhere.
Data in object based storage typically can’t be modified. Instead, modified files must be deleted and rewritten, each time leading to a new Object ID that must be stored for reference in the application.
While object storage was not designed to be used as a file system, some systems emulate a file system using object storage. For instance, Amazon’s S3FS creates a virtual filesystem, based on S3 object storage, that can be mounted to an operating system in the traditional way.
This entry was posted on Friday 07 October 2016
Software Defined Networking (SDN) is a relatively new concept. It allows networks to be defined and controlled using software external to the physical networking devices.
With SDN, a relatively simple physical network can be programmed to act as a complex virtual network. It can become a hierarchical, complex and secured virtual structure that can easily be changed without touching the physical network components.
An SDN can be controlled from a single management console and open APIs can be used to manage the network using third party software. This is particularly useful in a cloud environment, where networks change frequently as machines are added or removed from a tenant’s environment. With a single click of a button or a single API call, complex networks can be created within seconds.
SDN works by decoupling the control plane and data plane from each other, such that the control plane resides centrally and the data plane (the physical switches) remain distributed, as shown in the next figure.
In a traditional switch or router, the network device dynamically learns packet forwarding rules and stores them in each device as ARP or routing tables. In an SDN, the distributed data plane devices are forwarding network packets based on ARP or routing rules that are loaded into the devices by an SDN controller devices in the central control plane. This allows the physical devices to be much simpler and more cost effective.
Network Function Virtualization
In addition to SDN, Network Function Virtualization (NFV) is a way to virtualize networking devices like firewalls, VPN gateways and load balancers. Instead of having hardware appliances for each network function, in NFV, these appliances are implemented by virtual machines running applications that perform the network functions.
Using APIs, NFV virtual appliances can be created and configured dynamically and on-demand, leading to a flexible network configuration. It allows, for instance, to deploy a new firewall as part of a script that creates a number of connected virtual machines in a cloud environment.
This entry was posted on Friday 23 September 2016
Software Defined Storage (SDS) abstracts data and storage capabilities (the control plane) from the underlying physical storage systems (the data plane). This allows data to be stored in a variety of storage systems while being presented and managed as one storage pool to the servers consuming the storage. The figure below shows the SDS model.
Heterogeneous physical storage devices can be made part of the SDS system. SDS enables the use of standard commodity hardware, where storage is implemented as software running on commodity x86-based servers with direct attached disks. But the physical storage can also be a Storage Area Network, a Network Attached Storage system, or an Object storage system. SDS virtualizes this physical storage into one large shared virtual storage pool. From this storage pool, software provides data services like:
SDS provides servers with virtualized data storage pools with the required performance, availability and security, delivered as block, file, or object storage, based on policies. As an example, a newly deployed database server can invoke an SDS policy that mounts storage configured to have its data striped across a number of disks, creates a daily snapshot, and has data stored on tier 1 disks.
APIs can be used to provision storage pools and set the availability, security and performance levels of the virtualized storage. In addition, using APIs, storage consumers can monitor and manage their own storage consumption.
This entry was posted on Friday 09 September 2016
Originally, operating systems were designed to run a large number of independent processes. In practice, however, dependencies on specific versions of libraries and specific resource requirements for each application process led to using one operating system – and hence one server – per application. For instance, a database server typically only runs a database, while an application server is hosted on another machine.
Compute virtualization solves this problem, but at a price – each application needs a full operating system, leading to high license and systems management cost. And because even the smallest application needs a full operating system, much memory and many CPU cycles are wasted just to get isolation between applications. Container technology is a way to solve this issue.
The figure above shows the relation between isolation between applications and the overhead of running the application. While running each application on a dedicated physical machine provides the highest isolation, the overhead is very high. An operating system, on the other hand, provides much less isolation, but at a very low overhead per application.
Container technology, also known as operating-system-level virtualization, is a server virtualization method in which the kernel of an operating system provides multiple isolated user-space instances, instead of just one. These containers look and feel like a real server from the point of view of its owners and users, but they share the same operating system kernel. This isolation enables the operating system to run multiple processes, where each process shares nothing but the kernel.
Containers are not new – the first UNIX based containers, introduced in 1979, provided isolation of the root file system via the chroot operation. Solaris subsequently pioneered and explored many enhancements, and Linux control groups (cgroups) adopted many of these ideas.
Containers are part of the Linux kernel since 2008. What is new is the use of containers to encapsulate all application components, such as dependencies and services. And when all dependencies are encapsulated, applications become portable.
Using containers has a number of benefits:
- Isolation – applications or application components can be encapsulated in containers, each operating independently and isolated from each other.
- Portability – since containers typically contain all components the embedded application or application component needs to function, including libraries, patches, containers can be run on any infrastructure that is capable of running containers using the same kernel version.
- Easy deployment – containers allow developers to quickly deploy new software versions, as the containers they define can be moved to production unaltered.
Containers are based on 3 technologies that are all part of the Linux kernel:
- Chroot (also known as a jail) - changes the apparent root directory for the current running process and its children and ensures that these processes cannot access files outside the designated directory tree. Chroot was available in Unix as early as 1979.
- Cgroups - limits and isolates the resource usage (CPU, memory, disk I/O, network, etc.) of a collection of processes. Cgroups is part of the Linux kernel since 2008.
- Namespaces - allows complete isolation of an applications' view of the operating environment, including process trees, networking, user IDs and mounted file systems. It is part of the Linux kernel since 2002.
Linux Containers (LXC), introduced in 2008, is a combination of chroot, cgroups, and namespaces, providing isolated environments, called containers.
Docker can use LXC as one of its execution drivers. It adds Union File System (UFS) – a way of combining multiple directories into one that appears to contain their combined contents – to the containers, allowing multiple layers of software to be "stacked". Docker also automates deployment of applications inside containers.
Containers and security
While containers provide some isolation, they still use the same underlying kernel and libraries. Isolation between containers on the same machine is much lower than virtual machine isolation. Virtual machines get isolation from hardware - using specialized CPU instructions. Containers don't have this level of isolation. However, there are some operating systems, like Joyent SmartOS' offering, that run on bare metal, and providing containers with hardware based isolation using the same specialized CPU instructions.
Since developers define the contents of containers, security officers lose control over the containers, which could lead to unnoticed vulnerabilities. This could lead to using multiple versions of tools, unpatched software, outdated software, or unlicensed software. To solve this issue, a repository with predefined and approved container components and container hierarchy can be implemented.
Where an operating system abstracts resources such as CPU, RAM, and network connectivity and provides services to applications, container orchestration, also known as a datacenter operating system, abstracts the resources of a cluster of machines and provides services to containers. A container orchestrator allows containers to be run anywhere on the cluster of machines – it schedules the containers to any machine that has resources available. It acts like a kernel for the combined resources of an entire datacenter instead of the resources of just a single computer.
There are many frameworks for managing container images and orchestrating the container lifecycle. Some examples are:
- Docker Swarm
- Apache Mesos
- Google's Kubernetes
- Pivotal CloudFoundry
- Mesophere DC/OS
This entry was posted on Wednesday 22 June 2016
Identity and Access management (IAM) is the process of managing the identity of people or systems and their permissions on systems.
IAM is a three-way process. In an IAM solution, users or systems first announce who they are (identification – they provide their name), then their claimed account is checked (authentication – they provide for instance a password, which is checked), and then the account is granted the permissions related to their identity and the groups they belong to (authorization – they are allowed into the system).
Most systems have a way to connect identities and their permissions. For instance, the kernel of an operating system owns an administration of users and a list of user rights that describes which identities are allowed to read, write, modify, or delete files.
IAM is not only used on the operating system level, but also in applications, databases, or other systems. Often these systems have their own stand-alone IAM system, which leads to users logging in to each and every system they use. With Single sign-on (SSO), a user logs in once and is passed seamlessly, without an authentication prompt, to applications configured with it. SSO provides user friendliness, but does not necessarily enhance security – when the main login credentials are known, an attacker gains access to all systems. SSO is typically implemented using LDAP, Kerberos, or Microsoft Active Directory.
Federated identity management extends SSO above the enterprise level, creating a trusted authority for digital identities across multiple organizations. In a federated system, participating organizations share identity attributes based on agreed-upon standards, facilitating authentication from other members of the federation and granting appropriate access to systems.
Users can be authenticated in one of three ways:
- Something you know, like a password or PIN
- Something you have, like a bank card, a token or a smartphone
- Something you are, like a fingerprint or an iris scan
Many systems only use a username/password combination (something you know), but more and more systems use multi-factor authentication, where at least two types of authentication are required. An example is an ATM machine, where a bank card is needed (something you have) and a PIN (something you know).
Typically, users are members of one or more groups (typically named after their roles in the organization) and, instead of granting permissions to individual users, these groups are granted permissions. And since groups can be nested (a group is member of another group), this so-called Role Based Access Control (RBAC) is very powerful.
This entry was posted on Friday 01 April 2016