Interface Cards & Controllers

RAID Array Levels

There are many different types of RAID arrays and each particular setup has its own advantages, disadvantages and specialized uses. Any one of these levels may or may not be most appropriate for your system depending on how much data you need to store and how you plan to use that data. With that in mind, let's look at the most common RAID levels and the strengths and weakness of each configuration.

 

RAID 0

A RAID 0 setup splits data evenly among two or more hard drives. It does not allow for any parity information and therefore there is no data redundancy, which means that any disk failure will affect the entire system. The primary function of this specific design is to increase system performance.

Using a RAID 0 setup, you can only store as much data as allowed by the storage capacity of the smallest drive in your system. The more hard drives you use in this setup, the lower the reliability of the system, since the failure of one drive affects them all. The more drives you use, the more chance there is that something will go wrong and cause the entire system to fail.

 

RAID 1

A RAID 1 setup creates a mirror image or exact copy of a group of files on two or more disks. This array allows for redundancy, meaning that since the same data is stored on multiple drives so that if one drive fails, you can still retrieve the data from the other drive. With this type of system, unlike the above RAID 0, the more drives you have in your array the more reliable the system is. To lose all your data with a RAID 1, each and every drive in the system would have to fail – which is quite unlikely to happen at the same point in time.

However, like RAID 0, this system's storage capacity is again limited by the size of the smallest drive in the array. RAID 1 allows for better performance the more drives you have, since data can be read from more than one disk at a time.

 

RAID 2

RAID 2 uses a technique called striping, or allocating data among several hard drives at the bit level, as opposed to RAID 1 which creates the mirror image of whole blocks of data. This allows for extremely high rates of data transfer. This set up is now essentially obsolete due to the fact that all hard disks now have an error correction code that use similar technology to the RAID 2 without the added complexity.

 

RAID 3

Another obsolete and rarely used set up. It uses striping to allocate the data at the byte level, and designates a specific disk for storing parity information. One of the main deficiencies of RAID 3 is that it can't handle multiple requests for data simultaneously, which slows its performance compared to other set ups, like the RAID 1.

 

RAID 4

RAID 4 uses block level striping along with a dedicated parity drive. Each drive in the system can work independently and in most cases can handle multiple requests for data simultaneously. This set up requires a minimum of three hard drives for its configuration to work. With RAID 4, a substantial load is placed on the parity drive and it often becomes a bottleneck for the entire system. For this reason, the performance level of this type of array can be rather poor.

 

RAID 5

RAID 5 uses block level striping and distributes parity data among every drive in the array. This is a very popular configuration since it allows for greater data redundancy while still offering a high level of performance. RAID 5 implementation requires a minimum of 3 hard drives in the system, but, in theory, you could have an unlimited number of drives connected to the system.

RAID 5 can survive the failure of a drive in the system by using the parity and data blocks from the surviving disks to reconstruct the lost data while the system continues to run, and this feature is known as Interim Data Recovery Mode.  The operating system notifies the administrator that a drive needs to be replaced while continuing to run without any disruptions, though the systems performance will be somewhat slower due to the changed operation.

 

RAID 6

RAID 6 is an extension of RAID 5 that adds an additional parity block on each drive. This allows for continued performance in the event of two simultaneous drive failures.

 

There are several other non-standard RAID levels such as RAID 1.5, 7, 5E, 5EE, 6E and others, but these are more complicated and less common versions. The most popular levels of RAID today are RAID 0, 5 and 6. Having a RAID array in place can help to secure your data and protect it from loss in the event that you have a hardware or software problem.

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Data Recovery Specialist

5 Reasons Companies Utilise Virtual Servers To Supply Their Internet Presence

Virtual servers work great for the web developer that is short in the pocket. There are different types of VPS's available, the main ones being Linux virtual servers or windows virtual servers.

Virtual server hosting are frequently used for voice hosting. Voice server hosts spread their services all over the world- The UK, US, Canada and Australia. This makes virtual servers perfect. For a host, the cost of dedicated servers in each location is not practical. Virtual servers are a fraction of the cost and thus allow a host to have a worldwide presence.

Virtual hosting is mostly used for web hosting. Particularly for specialist companies that don't quite need a dedicated server. A VPS that is well setup will have a redundant hard disk array, as well as CPU and memory on demand. Those that just want to host a couple of websites also take virtual servers as an option. A VPS also isolated you from other web users. You cannot do this with normal web hosting.

Creators of social media apps also make use of virtual servers. Those Facebook addicts will be familiar with such apps. Facebook applications are used in their millions. You can do everything from managing an army, to a record company! Again the benefit for developers is they can host these applications on a virtual hosting environment without the need to opt for an overkill dedicated server environment.

Virtual servers are very often used for database environments. Never have all your eggs in one basket. Using virtual servers keeps databases offsite and safe.

DNS in this same respect benefits massively from the virtual server. I recently setup a backup DNS server at the fraction of the cost. Our main DNS is hosted onsite, but the secondary offsite. In the event our services go offline, we still have an NS2 that will serve DNS from a different network, and a different datacentre. This allows for much better uptime.

We have identified the 5 main uses for virtual servers above. If we've missed anything out, please do let us know below.

IT Expert help on setting raid array in linux?

What must be done when setting up a RAID array in Linux?
A) All the disks must be partitioned as primary partitions.
B) All the partitions need an extended partition.
C) The disks must be mounted using LVM.
D) The disks must be formatted using NFS.

Try asking in the Linux section of Slashdot.org

A New Cloud Drive With a Twist From Pogoplug (readwriteweb)

Yesterday, Richard's cloud drive article makes note of Dropbox and Google Docs
and other cloud storage providers. There is a new take on this from a company
called Cloud Engines with their Pogoplug service. It combines the typical
cloud drive with a piece of hardware. Here is how it works.

_Sponsor_

You purchase the device, called Pogoplug Mobile for $80. It is about the size
of a small paperback, and has ports for SD and USB drives, wired Ethernet and
power. Before you hook everything up, you can use either the SD card or a
standard USB thumb drive to store backup copies of your files. Next, you
connect it to your network and hence to the Internet, register the device and
download client software to add other files.

Once you activate your device, it will take some time before you can see the
files that are stored on it. This is because Pogoplug is running its
equivalent of CHKDSK on the files on your storage media.

Why is it called Mobile? That is somewhat confusing, as the device doesn't
move about: it remains connected to your broadband Internet home or office
network. Nevertheless, the idea ...

readwriteweb

How to set up a RAID array on your motherboard