Modern DAS systems. Comparative characteristics of data storage systems

During most of the 2000s, most computer-owning families had only one PC with one hard drive. If you needed to store data beyond the capacity of your hard drive, you typically burned it to a CD. But it was slow, cumbersome, and a waste of physical space.

It was around this time that external drives gained popularity and became the norm. For a long time, external devices have been the choice for consumers with large amounts of storage and data transfer.

But as multi-computer, multi-user devices, where one person uses multiple computers, has become the new normal, external hard drives can no longer meet all needs.

Network or cloud storage is the future and there are four main types: cloud, NAS, DAS and SAN.

General information about cloud (network) storage (cloud)

Now cloud storage is very fashionable. It fulfills many of the same needs as external drives and offers more features and convenience. In short, cloud storage is when you store your data on a cluster of remote servers (the "cloud") that are accessed over the internet.

Instead of keeping an external drive connected to your system and taking up precious space, you simply create an account and download files whenever you need to. No USB charging ports. No additional energy use. And if your house burns down, your data will still exist on remote servers. Most cloud storages offer automatic synchronization, which is even more convenient.

But cloud storage has its drawbacks. If your internet connection goes down, you lose access to your data. USB transfer speeds are much faster than most Internet connections, so uploading and downloading to the cloud takes longer than external drives. And the privacy of your data uploaded to the cloud is still a major concern. Are cloud storage services peeking into your data? Or even sell this data? We cannot know for sure.

For many, the convenience outweighs the risk. That's why services like Dropbox, Google Drive, Yandex Drive, and OneDrive are so popular right now. Free storage is plentiful, but if you need a lot of space, storage can cost anywhere from $2 to $100 per month.

General information about NAS storage

If you love your external drives and can't let them go, let me introduce Network Attached Storage (NAS) to you. This is what you would get if you took an external drive and made it available to more than one device at a time. Sounds great, right?

NAS is about the same as an external drive, only bigger and more functional. And instead of connecting to one device at a time with a USB cable, it mounts on the local network. Ethernet is the most common and preferred method, but some may connect it via Wi-Fi.

Functionally speaking, you interact with the NAS just like you would with an external drive. Once it's connected to your network, you can access it much the same way (except you'll go to Network instead in File Explorer). But the real benefit is that you can access it from any device!

And if you've set up your network for remote access, you can access the NAS from anywhere as long as you have an Internet connection, leveraging cloud storage features without the privacy-related drawbacks.

NAS devices can cost anywhere from $150 to $600 depending on how much advanced functionality you want. Please note that the NAS is just a "shell", so you will have to buy the drives separately and insert them yourself.

Introduction to SAN storage (Storage Area Network)

What happens when one NAS doesn't provide enough capacity? One option is to build a NAS, but this can be inconvenient in some cases as they each work independently with separate IP addresses and separate settings.

Another option is to use a storage area network (SAN). NAS, SAN offloads data storage from desktops and server machines to dedicated storage devices. But while a NAS is an independent device, a SAN is a network of interconnected storage devices. They are accessed through the local network to which they are connected.

The biggest difference is that SANs are lower end than NAS. Data on a NAS is managed by the NAS itself and is thus represented as "files", while data on a SAN is raw and available as "blocks". Practically speaking, NASES appear as "file servers" and SANs appear as "disk" or "disks". And instead of using TCP/IP, SANs use other network protocols such as Fiber Channel and iSCSI.

Today's SAN storage can store many terabytes of data on a device and is unlikely to be needed by the average home user. Just add a second or third drive to the NAS. For this reason, and the need to connect to protocols other than TCP/IP, SANs are primarily used by enterprises, data centers, and other large organizations.

Understanding DAS storage

Now we're back to where we started. If you want to get rid of all the above NAS options, the only alternative is Direct-attached storage (DAS). As the name implies, a DAS needs to be physically connected to any device that wants to access its data.

You use DASES every day. All examples of DAS are hard drives, CD/DVD drives, flash drives, and external drives. In fact, the term DAS was created after the advent of NAS and SAN to differentiate between network storage and non-network storage.

These days, DAS is increasingly referred to as a distinct cluster of non-network business-class clusters. For example, Lenovo E1012 DAS is suitable for 12 drives. Think of them like massive external drives. No wonder they are nicknamed JBOD ("just a bunch of disks").

But DAS options also exist at the consumer level. Noontec-TerraMaster D5-300 DAS fits up to five storage drives and connects to USB Type-C. Just don't expect it to deliver the transfer speeds of business class DAS that use SAS connectors instead of USB.

Which type of NAS is right for you?

For typical home users, only two of these options are viable: cloud storage and NAS storage.

While NAS storage is objectively superior, it is better suited for users familiar with the technology. Setup is a bit more involved than installing a plugin or game, and requires regular care and maintenance if you want it to last for a while. It's also cheaper in the long run compared to paid cloud storage services.

But cloud storage is easier. Just install the required software and you can upload your files to the cloud. There are no settings, no maintenance, and if you're not going to store terabytes of data there, then no fees. If you're willing to risk your privacy, and if you don't mind having no access when your internet isn't available, then cloud storage can be a great option.

Where do you store your data? Have you already used a NAS? Or are you still relying on external drives and/or the cloud? Share with us in the comments below!

Direct Attached Storage Systems (DAS) implement the most well-known type of connection. When using DAS, the server has a personal connection to the storage system and is almost always the sole user of the device. In this case, the server receives block access to the data storage system, that is, it accesses data blocks directly.

Storage systems of this type are quite simple and usually inexpensive. The disadvantage of the direct connection method is the small distance between the server and the storage device. A typical DAS interface is SAS.

Network Attached Storage (NAS)

Network-attached storage systems (NAS), also known as file servers, provide their network resources to clients over the network in the form of shared files or directory mount points. Clients use network file access protocols such as SMB (formerly known as CIFS) or NFS. The file server, in turn, uses block access protocols to its internal storage to process file requests from clients. Because the NAS is networked, the storage can be very far away from the clients. Many networked storage systems provide additional features such as storage imaging, deduplication or data compression, and others.

Storage Area Network (SAN)

A storage area network (SAN) provides clients with block access to data over a network (such as Fiber Channel or Ethernet). Devices in a SAN do not belong to a single server, but can be used by all SAN clients. It is possible to partition disk space into logical volumes that are allocated to individual host servers. These volumes are independent of the SAN components and their placement. Clients access the storage using a block type of access, just like a DAS connection, but since the SAN uses a network, storage devices can be located far from the clients.

Currently, SAN architectures use the SCSI (Small Computer System Interface) protocol to transmit and receive data. Fiber Channel (FC) SANs encapsulate the SCSI protocol in Fiber Channel frames. SANs using iSCSI (Internet SCSI) use TCP/IP packets as the SCSI transport. Fiber Channel over Ethernet (FCoE) encapsulates the Fiber Channel protocol into Ethernet packets using the relatively new DCB (Data Center Bridging) technology, which brings a set of improvements to traditional Ethernet and can currently be deployed on 10GbE infrastructure. Because each of these technologies allows applications to access the data store using the same SCSI protocol, it becomes possible to use them all in one company or migrate from one technology to another. Applications running on the server cannot distinguish between FC, FCoE, iSCSI, and even distinguish DAS from SAN.

There are many discussions regarding the choice of FC or iSCSI for building a storage area network. Some companies focus on the low initial deployment cost of an iSCSI SAN, while others choose the high reliability and availability of a Fiber Channel SAN. Although low-end iSCSI solutions are cheaper than Fiber Channel, as the performance and reliability of iSCSI SANs increases, the price advantage disappears. However, there are some FC implementations that are easier to use than most iSCSI solutions. Therefore, the choice of a particular technology depends on business requirements, existing infrastructure, expertise and budget.

Most large organizations that use SANs choose Fiber Channel. These companies typically require proven technology, need high bandwidth, and have the budget to purchase the most reliable and capable hardware. In addition, they have the staff to manage the SAN. Some of these companies plan to continue investing in Fiber Channel infrastructure, while others are investing in iSCSI solutions, especially 10GbE, for their virtualized servers.

Smaller companies are more likely to choose iSCSI because of the low entry price point, while still being able to scale the SAN further. Low cost solutions typically use 1GbE technology; 10GbE solutions are significantly more expensive and are generally not considered entry-level SANs.

unified storage

Universal storage systems (Unified Storage) combine NAS and SAN technologies in a single integrated solution. These versatile storages allow for both block and file access to shared resources and are easier to manage with centralized management software.

Was ist DAS?

CFI B8253JDGG or NAS server?

Both DAS and NAS devices are storage devices. However, the NAS server has one important property: unlike the DAS, the NAS server is a standalone device, and has everything you need for standalone operation: a network interface, software, a hardware control part, and in some cases even a display. The NAS server can be used without a computer - for example, remotely save vacation photos from a smartphone, or watch movies from a home collection at the workplace from a tablet by connecting to the NAS server as a "cloud".

In turn, a DAS drive (Direct-attached storage abbreviation) is not capable of any conscious independent actions, however, in most cases it is more convenient and profitable. DAS is an external box with a hardware RAID controller with convenient access to hard drives, which must be connected to the USB or eSATA port of a computer, laptop or router with USB storage support.

Despite the fact that DAS is a simpler drive, it will cope with the vast majority of data storage tasks just as well as a NAS server. At the same time, it has an attractive price and a lot of really useful functions.

DAS CFI B8253JDGG + router: personal cloud storage

Equipping the CFI B8253JDGG DAS with personal cloud storage is a breeze. All it takes is a more or less decent router with support for host devices. Connect DAS CFI B8253JDGG to your router and access your home collection of movies, music and photos from anywhere, at any time of the day or night, for free and without registration.

Create your own cloud storage, the reliability of which you will be completely sure, and the volume of which will depend only on your needs. Five slots for hard drives larger than three terabytes with automatic RAID creation and background array rebuilding - no Google Drive will give such an effect.

The characteristics of the CFI B8253JDGG DAS drive are shown in the table below.

DAS CFI B8253JDGG + Computer: Valuable Data Backup

The time when the family archive was kept in a couple of albums on dusty mezzanines has passed. A modern home storage of photos, videos of celebrations and holidays and other memories dear to the heart is a DAS connected to a computer or laptop. The area occupied by it is negligible compared to tens of terabytes of information that you can without noise and dust for many years.

Storing valuable data in a laptop is convenient, but unsafe. A collection of favorite movies or photos can be irretrievably lost when the drive fails, and valuable work information will be lost forever along with the laptop itself in the event of a breakdown or theft of the latter. To ensure that your work and personal information is always safe and sound, you need to back up your data (backup). Is always.

With the CFI B8253JDGG DAS, your data is always secure. Thanks to the automatic creation of a RAID array, you can always duplicate information from the drives of a computer or laptop to a DAS, in the disks of which, in turn, information will also be duplicated on several disks. Supported RAID 5, 3, 10, 1, 0 and JBOD formats allow you to create a fast, reliable or very reliable array, and restore all your work and personal information even if several hard drives fail at once.

CFI B8253JDGG + NAS: An affordable way to double your NAS capacity

The CFI B8253JDGG External Box is the most cost-effective way to expand the available storage capacity of your server, workstation, and NAS storage. Sooner or later, the capacity of your existing file server or media storage will not be enough, and you will have two options: buy a second NAS for a lot of money or expand the capacity of your existing server with a DAS drive. Of course, it is better to choose the second option.

One or more DAS drives connected to a NAS server allow you to increase its usable volume by several times. At the same time, DAS CFI B8253JDGG will be endowed with the full functionality of an existing NAS server: access from mobile devices, downloading files without a computer, and much more - depending on the capabilities of the NAS. By connecting a 5-disk DAS CFI to a single-disk NAS server, you will have a 6-disk NAS available to all users of your network. When connected via a high-speed eSATA port, access to the external CFI DAS module will be as close as possible to the access speed of the hard drive built into the NAS.

When the task of backing up a multi-disk network storage, network video recorder (NVR) or server, for example, to 5 - 8 hard drives, the problem of acquiring proportional capacity automatically arises. With a head-on approach, the decision is equal to buying a second NAS (NVR) for 5 - 8 disks. Which is really expensive. And here DAS CFI comes to the rescue, which, with equal 5 disks, is half the price of a 5-disk NAS.

Simply connect the CFI B8253JDGG External RAID Drive to any network storage device via eSATA or USB interface, insert hard drives, select a storage mode and power up the B8253JDGG. Ease of setup, fast hot-swappable drives, and versatile connectivity make the CFI B8253JDGG External RAID Containers a safe place to store your information. And the low price will make enterprise-level reliability available to all private users.

The working repository of a freelancer and a real designer

The CFI B8253JDGG DAS is not only reliable, but also very fast. Equipped with USB 3.0 and eSATA ports, the CFI B8253JDGG provides the highest data transfer speed when connected to a PC or laptop. The data exchange rate between the computer and the CFI B8253JDGG external drive connected to it via USB 3.0 exceeds 200MB / s.

This is more than enough for a quick backup of layouts, transferring footage from a wedding for later editing, or for replicating a catalog to several hard drives at once. Ideal for high volume productive work such as video editing, printing and industrial design.

To simultaneously access multiple storage HDDs from a PC, server, or NAS, you just need to set the CFI drive to CLEAN mode and connect it to the host device, changing the desired drives as needed.

In this article, we will talk about DAS. Distributed Antenna System or Distributed Antenna System. Consider these questions:

Basic understanding of DAS

Components of a DAS

Application

Signal sources

The three main types of DAS along with their pros and cons

Collaboration of various participants for DAS deployment

DAS is defined as a converged single signal transmission medium connecting spatially separated antennas that provide users with wireless access within a building or area. (Convergence is a property of the system, roughly speaking, to transmit voice, data, etc. via one cable).

A DAS can be designed to support multiple providers at once, allowing it to operate across different frequency bands and different technologies. From here we see the important properties of DAS - scalability and flexibility.

What is DAS made of?

Here, the signal source does not imply the generation of a cellular signal. The signal must be given in some way. The two most common are:

• The signal comes from a transceiver antenna on the facade of the building
• The signal is sent from the local base station of the mobile operator, the so-called on-site BTS

Signal flow

DAS applied at various public and social facilities: business centers, hospitals, universities, stadiums, hospitals. The application of DAS can be considered in terms of the ratio the quality of the radio signal coverage and the maximum subscriber load. Some objects experience significantly higher data transfer loads than others. For example, a stadium hosting a sporting event or concert will not be able to provide all visitors with communication using a single cell tower. In this case, DAS will help to cope with high subscriber load. On the other hand, subscribers may experience low signal strength due to remoteness of the base station or due to shielding. In practice, most often one has to deal with shielding caused by Low-E glass, which is used to glaze the facades of business centers. Using a special method, thin layers of rare-earth metals are sprayed onto finished glass, and after a special composition of these glasses, a window is obtained that provides comfortable climatic parameters of the environment inside the building, however, the signal level inside the building drops sharply, and employees walk “with one stick” on their smartphone. DAS eliminates this drawback of Low-E glass and provides the building with a high-quality coating.

Signal sources

Front donor antennas

local base station

femtopoint network

Wireless signal transmission

In this type of DAS, a donor antenna is used, installed on the roof or facade of the building (on the engineering floor), which receives the signal from the base station of the mobile operator. In cases where the signal from the tower is strong and clear, this type of source signal provision is most often used. It can be seen that in this case, the installed DAS will not expand the local capacity of the operator's network.

local base station

Base Transmitting Station (BTS, NodeB, eNodeB) is equipment whose main tasks are to convert the signal received from the cellular operator into a high-frequency signal and transfer it to the subsequent module. The connection of the BS and the core of the operator's network is carried out via optics (these works are most often performed by the operator himself). International hub airports may use several local base stations to serve tens of thousands of passengers. A DAS using the BTS signal takes longer to deploy and costs significantly more (BTS is expensive in itself, and each operator still has to extend the optics).

In practice, it is possible to combine the solutions described above, depending on the power and quality of the operators' signal.

There are three types of DAS:

• Passive
• Active
• hybrid

Passive DAS.

Uses a coaxial cable to transmit the signal to each floor of the building (the area that needs coverage). It consists of various types of passive elements: couplers (couplers), splitters (splitters) and dividers (dividers). These passive elements “take a portion” of the signal for each floor, the distribution of the overall signal power was pre-calculated by engineers, and passive elements were selected in accordance with these calculations. A passive DAS has no active electronic components.

Active DAS

Hybrid DAS

How does DAS appear?

Telecommunications operator

Sets system design standards

Invests in DAS

Provides signal source

• Production and supply of the central control unit, remote access units and other devices necessary for a specific task

Third Party DAS Operator

Maintains facility cabling systems

Allocates space for deploying DAS infrastructure

Serves and manages DAS after deployment

System integrator

Responsible for design, installation and commissioning

Serves as a link for all participants in the DAS deployment process

Common design options

Passive Wireless DAS

It costs less than other types of DAS, is quickly deployed (the need to provide communication to several operators requires more time resources). You need a powerful and high-quality signal from the operator's tower.

Hybrid Wireless DAS

Hybrid DAS combines the ability of active DAS to cover large areas, but with the economic benefits of a passive system.

Active/Hybrid System with BTS (Local Base Station)

A coverage map of mobile operators is needed to select an operator in your area, according to the level of communication provided. The map is regularly updated to keep it current.

The strategy of any business is to reduce risks and increase profits. One way to achieve this goal is to develop the right policy for corporate information management and storage. Information is the driving force behind modern business and is considered the most valuable strategic asset of any enterprise. The volume of information is growing exponentially along with the growth of global networks and the development of e-commerce. Success in business requires an effective strategy for storing, protecting, sharing, and managing data. According to IDC, over the past ten years, out of 40% of American companies that completely lost their data as a result of neglect of storage technologies, only 10% were able to return to business and only 4% (!) Of them survived over the next three years.

Storage resource management has become one of the most pressing issues facing IT departments. Due to the development of the Internet and fundamental changes in business processes, information is accumulating at an unprecedented rate. In addition to the urgent problem of ensuring the possibility of a constant increase in the volume of stored information, the problem of reliable data storage and constant access to information is no less acute on the agenda. For many companies, the “24 hours a day, 7 days a week, 365 days a year” data access formula has become the norm.

The most important elements of the information network today are servers, data storage systems (DSS) and technologies for their administration.

Failure leads to a temporary suspension of business processes and partial (or complete) loss of data and calls into question the existence of the business as a whole.

One of the largest consumers of servers and storage systems in Russia is traditionally the public sector. In second place in terms of consumption is the telecommunications and oil and gas industries, followed by financial organizations (primarily banks and industry). This distribution is quite stable and has been maintained over the past years.

Today, we can single out one traditional one - Direct Attached Storage (DAS) and two storage architectures that are already confidently entering life - Network Attach Storage (NAS) and Storage Area Network (SAN).

Direct Attached Storage (DAS)

DAS technology implies a direct (direct) connection of drives to a server or to a PC. In this case, drives (hard drives, tape drives) can be both internal and external. The simplest case of a DAS system is a single disk inside a server or PC. In addition, the organization of an internal RAID array of disks using a RAID controller can also be attributed to a DAS system.

It is worth noting that, despite the formal possibility of using the term “DAS systems” in relation to a single disk or an internal array of disks, a DAS system is usually understood as an external rack or basket with disks, which can be considered as a stand-alone storage system. In addition to independent power supply, stand-alone DAS systems have a specialized controller (processor) for managing an array of drives. For example, a RAID controller with the ability to organize RAID arrays of various levels can act as such a controller.

It should be noted that stand-alone DAS systems can have several external I/O channels, which makes it possible to connect several computers to the DAS system at the same time.

SCSI (Small Computer Systems Interface), SATA, PATA and Fiber Channel interfaces can act as interfaces for connecting drives (internal or external) in DAS technology. While SCSI, SATA, and PATA interfaces are primarily used for connecting internal drives, the Fiber Channel interface is used exclusively for connecting external drives and stand-alone storage systems. The advantage of the Fiber Channel interface here is that it does not have a hard length limit and can be used when the server or PC connected to the DAS system is located at a considerable distance from it. SCSI and SATA interfaces can also be used to connect external storage systems (in this case, the SATA interface is called eSATA), but they have a strict limit on the maximum length of the cable connecting the DAS system and the connected server.

The main advantages of DAS systems include their low cost (compared to other storage solutions), ease of deployment and administration, and high speed of data exchange between the storage system and the server. Actually, it is for this reason that they have become very popular in the segment of small offices and small corporate networks. At the same time, DAS systems have their drawbacks - first of all, this is the high cost of storing and managing data due to their dispersion throughout the organization, as well as the forced downtime of the network when new disks are added and the need to increase the memory or processor power of the server when a certain size is exceeded. disk space. Congestion of network traffic with the addition of new servers complicates the problem of data protection, hinders the efficient use of resources, etc. Costs and new problems are snowballing.

Currently, DAS systems occupy a leading position, but the share of these systems is constantly declining, and they are being replaced by either universal solutions with the ability to smoothly migrate to NAS systems, or systems that provide for the possibility of using them both as DAS and NAS - and even SAN systems.

Network Attached Storage (NAS)

NAS systems are network attached storage systems that are directly connected to the network in the same way as a network print server, router or any other network device. In fact, NAS systems are an evolution of file servers. To understand the difference between a traditional file server and a NAS device, remember that a traditional file server is a dedicated computer (server) that stores information available to network users. To store information, hard drives installed in the server (as a rule, they are located in special baskets) or DAS devices connected to the server can be used. The administration of the file server is implemented using the server operating system. This approach to organizing data storage systems is currently the most popular in the segment of small local networks, but has one significant drawback. The fact is that a universal server (and even in combination with a server operating system) is by no means a cheap solution. At the same time, most of the functionality inherent in the universal server is simply not used in the file server. The idea is to create an optimized file server with an optimized operating system and a balanced configuration. It is this concept that embodies NAS devices, which in this sense can be considered as thin file servers, or, as they are also called, filers.

In addition to an optimized OS, freed from all functions not related to file system maintenance and data I / O implementation, NAS systems have an access-optimized file system. NAS systems are designed in such a way that all of their computing power is focused solely on file serving and storage operations. The operating system itself is located in flash memory and is preinstalled by the manufacturer. Connecting NAS devices to the network and configuring them is a fairly simple task and within the power of any experienced user, not to mention the system administrator.

Compared to traditional file servers, NAS devices are more powerful and less expensive. Currently, almost all NAS devices are designed for use in Ethernet networks (Fast Ethernet, Gigabit Ethernet) based on TCP/IP protocols. NAS devices are accessed using special file access protocols. The most common file access protocols are CIFS, NFS, and DAFS.

Storage Area Network (SAN)

SAN is a specialized storage network infrastructure (SAN). These networks are integrated as separate specialized subnets into a local area (LAN) or wide area (WAN) network.

Essentially, SANs link one or more servers (SAN servers) to one or more storage devices. SANs allow any SAN server to access any storage device without loading other servers or the local network. In addition, it is possible to exchange data between storage devices without the participation of servers. SANs allow a very large number of users to store information in one place (with fast centralized access) and share it. RAID arrays, various libraries (tape, magneto-optical, etc.), as well as JBOD systems (disk arrays not combined in RAID) can be used as data storage devices.

To build SANs, either the Fiber Channel (FC) standard or the iSCSI standard is used.

What to choose - DAS, NAS or SAN?

Until now, all over the world, and even more so in Russia, DAS still dominates. This situation is likely to continue in the market segments of home computers, small businesses and large machines (mainframes). The niche of medium and large enterprises will gradually be occupied by SAN and NAS systems, and in combined use.

It is expedient to use SAN systems where data access is carried out at the level of physical blocks. We are talking primarily about distributed databases built on a client-server architecture. These are enterprise management systems, banking and financial systems, where the number of transactions per unit of time is critical, digital television broadcasting, etc. In addition, SAN systems are used to ensure the uninterrupted and uninterrupted operation of critical applications, the failure of which can lead to the loss of critical data, equipment failure, or other consequences that entail costly downtime of the information system. SAN is an excellent solution for organizations located in buildings scattered within a radius of up to 20 km, which need quick access to a central storage.

The use of SAN architecture is effective in organizing data centers with ever-increasing requirements for computing resources and storage capacity. The use of SAN allows solving such problems without fundamental modification of the existing infrastructure, thanks to the combination of Fiber Channel, SCSI and Ethernet network interfaces.

NAS systems are used in cases where data is accessed at the file level, these are business applications with simultaneous access of users of different platforms to the same files (multimedia, graphics, documents), consolidation of disparate enterprise information in one place, storage of archives, fast, inexpensive and license-free increase in disk space on the network.