Century IT blog

RAID (redundant array of independent disks)

July 2nd, 2012

What is RAID?

To answer it shortly, RAID stands for Redundant Array of Inexpensive/Independent Disks.

 

This doesn’t really answer the question though, because if you look into it a bit more, it’s easy to see that there is more to RAID than first meets the eye.

 

RAID comes in different levels, ranging from RAID 0 all the way to RAID 10. Although RAID levels 8 and 9 do not exist. Each of these RAID levels work in a different way to each other. I will go over how RAID levels 0, 1, 5 and 10 (RAID 10 also known as RAID 1+0 or 0+1).

 

RAID 0

 

 

RAID 0

RAID 0 is largely used to increase the performance and speed from a collection of hard disks. It works by striping data across the disks, sharing the data as if the two disks were just one. The major downside to this particular level of RAID, is that if one disk goes down, then you have lost all of the data even though one or more disks may still be perfectly healthy. This is no different however, to just having a single hard disk in your computer failing, causing you to lose whatever data was stored on it should you not have backed it up.

 

 

 

 

RAID1

 

RAID 1

The next level of RAID, is RAID 1. This works differently as it mirrors the data across however many disks are in the RAID, creating an exact copy on each disk. This is of course very useful should you store important data across this RAID setup, as if one of the disks were to fail, then you would have lost no data at all, as one of the other disks in the array will still have an exact copy of the data.

This array is only as large as the smallest disk in the array. This means that if you have two 500GB drives and a 250GB drive in the array, the RAID will only be 250GB, disregarding the remaining space left on the two 500GB drives.

 

 

 

RAID 5

The next level of RAID to look at is RAID 5. This type of array is one of the most popular as it provides good performance, good fault tolerance and allows for high storage amounts as well as having an exceptional read speed. Writing speed to the array however does suffer a fair amount so is not the best choice for a write intensive application, though if the array was used to host a database, RAID 5 would be an almost perfect choice.

 

 RAID5

 

 

RAID 10

Finally, there is RAID 10. Also known as RAID 1+0 or 0+1, this particular level of RAID array is generally regarded as the best. On the downside, it is also the most expensive form of RAID array to set up due to the fact that a minimum of 4 disks must be used. The reason behind RAID 10 being called either RAID 1+0 or 0+1, is because it’s simply a combination of RAID 1’s best features and RAID 0’s best features. This means that the data is both mirrored across drives as well as being striped leading to both very quick read speeds as well as fast write speeds. If you can afford to set up a RAID 10 array, then it is definitely the one to go for as it also allows for disk failures without loss of data.

 

RAID10

 

Hot Spare 

In the unfortunate event that a disk should fail in the array, you can also include what are called “Hot Spare” drives. These drives sit idle and unused until the failure of one of the disks in the array occurs. When one does, the Hot Spare drive then becomes active as it is then included as part of the array in place of the disk that was lost.

 

 

Summary

The above explanations try to clarify what RAID is and identify the benefits of each level of RAID. The subject of computer hardware specifications and the specifics of the types of disks and RAID levels available can be confusing and we would encourage you take advice from an I.T Expert before deciding upon the hardware specfication of a replacement server.

 

We offer FREE, confidential,  no obligation advice, so why not give us a call.

 

 

Century IT Services – Getting IT Right

Providing Computer Support & IT Support to businesses in Hampshire, Dorset, Surrey, Wiltshire, Sussex & Berkshire

 

 

Securing a Wireless Access Point

January 17th, 2012

 

From a network security point of view you should assume that every Wi-Fi system is insecure! Yours included!

 

Really!

 

By leveraging the technology built into wireless access points and routers you can make your Wi-Fi system more and more secure but it’s ‘safe’ to say that anyone with enough time and resources will be eventually be able to circumvent your Wi-Fi security and gain access to your network.

 

By properly securing your Wi-Fi you can make it more difficult and time consuming for a hacker to breach your Wi-Fi security and hopefully less likely to want to spend the time on your Wi-Fi system and move onto an easier target.

 

The time a hacker can take to break into your Wi-Fi system increases significantly if you implement the following technologies:-

 

  • Increasing Wi-Fi Encryption Level
  • MAC Address Filtering
  • Binding IP Address to MAC Address
  • Hiding a SSID
  • Replace old hardware which only works on WEP

 

In the same context that any internet connected computer’s security can be breached, any Wi-Fi system’s security can be breached.

 

If you need help or advice securing your network, give us a call. We don’t just do Wi-Fi but are experts in computers, networks, servers, internet and email.

 

 

Century IT Services – Getting IT Right

Providing Computer Support & Network Support to businesses in Hampshire, Dorset, Surrey, Wiltshire, Sussex and Berkshire.

USB 1.0 vs USB 2.0 vs USB 3.0

October 3rd, 2011

Introducing USB3.0
Since around 2005, USB2.0 has been the dominant standard for connecting external devices such as hard disks, tape drives, digital cameras, memory sticks, wireless cards etc. If you have connected any external device to a computer over the last 7 years, the chances are that you will have used USB2.0

Over the last couple of years, USB 3.0 has begun to emerge. Any newly purchased computer will have USB3.0 ports.

 

The main improvement is transfer speed: USB2.0 has a maximum speed of 480 mbps (megabits per second), whereas USB3.0 is capable of a whopping 5 Gbits/s (5000 mbps), or a 10x speed increase. This means that if it takes an hour to transfer some data to a USB2.0 device, it could take as little as 6 minutes using a USB3.0 device.

 

 

As with previous versions, USB3.0 is fully backwards compatible, therefore any USB2.0 device will work when plugged into USB3.0 ports.

 

 

Another major advantage is that USB3.0 devices will work with USB2.0 ports, though obviously at a decreased transfer speed. Therefore, it will not be necessary to replace computers, or add an expansion card, just to use these new devices.

 

Century IT Services – Getting IT Right
Providing Computer Support & Network Support to businesses in Hampshire, Dorset, Surrey, Wiltshire, Sussex & Berkshire.

USB 1.0 vs USB 2.0

September 14th, 2009

Most computers or laptops nowadays usually have a selection of USB ports that you can plug external devices into to extend the functionality of your computer system i.e. external hard disks, external tape drives, digital cameras, memory card readers, USB memory sticks etc.

 

Modern computers and laptops usually come with USB 2.0 ports as standard, whilst older computers only have USB 1.0Computer Support, Network Support, Server Support

 

As with all technology, advances have been made over the years to improve speed and performance. To maintain backward compatibility, newer types of USB ports come with the same type of connector as the older USB ports, so older USB devices can still connect and operate.

 

 

The main difference between USB 1.0 and USB 2.0 is the performance or throughput; the USB 2.0 ports are much faster than the earlier USB 1.0. USB 2.0 has an maximum throughput of around 480 mps (megabits per second) whilst USB 1.0 only has an average throughput of 12 mbps. That makes USB 2.0 as much as 40 times as quick as the older USB 1.0

 

This means that if it takes around 40 minutes to transfer some files to a USB 1.0 device, using USB 2.0 it could potentially take only 1 minute.

 

Century IT Services – Getting IT Right

Providing Computer Support & Network Support to businesses in Hampshire, Dorset, Surrey, Wiltshire, Sussex & Berkshire.

SATA vs SAS what are the benefits?

August 18th, 2009

SATA VS SAS

For many, there can be a lot of confusion when comparing different types of server solutions especially when it comes down the type of hard drives that your server might come with.

A server with SATA hard drives can be considerably cheaper when compared to a server with SAS hard drives, especially if your server quote has multiple hard drives or has a RAID disk subsystem. But this seemingly interchangeable terminology can make all the difference to your IT investment.

SATA – Serial ATA

SAS – Serial Attached SCSI

Serial ATA was designed to replace the older IDE (EIDE) hard drives which were commonly found in most home computer and business workstations.

SAS has evolved separately from the SCSI standard, SCSI drives have traditionally been found in server solutions.

Many server manufacturers including HP and Dell offer entry level servers with SATA drives, with the mid-range and higher end servers coming with SAS hard drives.

According to Seagate, SATA drives are designed to have the following features:-

Computer Support, Network Support

  • Capacity intensive
  • Low availability
  • Sequential reads
  • Seek time 9.5ms
  • Designed to be on 8 Hours a day, 5 days a week

Seagate SAS drives are designed for:-

  • Performance Intensive
  • High Availability
  • Random Reads
  • Seek time of 3.5 ms (15k rpm), 3.9 ms (10k rpm)
  • Designed to be on 24 hours per day, 7 days per week

From a computer support or network support point of view, many SAS drive solutions also include ‘hot swap’ options which basically mean that for many RAID solutions, you can simply replace a failed drive for a replacement without rebooting or interrupting the server or users.

What does all this mean?

Basically if you want good server performance and you don’t want disk I/O bottlenecks and prefer longevity over small price difference, always choose SAS over SATA.

If your requirements are for a small server in a very small office and are not worried about server performance and the larger capacity, cheaper SATA drives appeals to you then choose SATA.

Did you want to discuss your server requirements? For an informed opinion on server specifications and many other IT support subjects ‘Contact Us’

Century IT Services are Expert, Responsive and Flexible

For more Information on SATA vs SAS see the following links

http://www.seagate.com/

Seagate SAS VS SATA

Century IT Services – Getting IT Right
Providing Computer Support & Network Support to businesses in Hampshire, Dorset, Surrey, Wiltshire, Sussex & Berkshire

HP2600N Print Quality Problems

January 23rd, 2009

Ever had a problem with a HP2600N colour laser printer where the Magenta is faded, even when you print the demo pages or supplies status print outs the Magenta is faded or washed out?

 Microsoft Partner

The self test and cleaning page come out fine?

 

There seems to be a design flaw with these printers. The Magenta cartridge sits in the bottom of the printer and over a period of time, Magenta toner leaks out through apparent normal use.Microsoft Small Business Specialist

 

Toner dust builds up on the mirrors and lens inside the laser unit causes the fading. The only way to resolve this problem is to get the lens and mirrors cleaned.

 

I would advise getting this work carried out by a skilled technician, this procedure is not for the in-experienced. Incorrect repair of the laser unit can cause blindness , cancer or electric shock.

 

 

Century IT Services – Getting IT Right
Providing Computer Support & Network Support to businesses in Hampshire, Dorset, Surrey, Wiltshire, Sussex & Berkshire

60 Second Cram of tape drive capacities

December 7th, 2008

203_tandberg-lto-2-hh-external-drive-frontDDS/DAT Drives

DDS1   2GB/4GB

DDS2   8GB/16GB

DDS3   12GB/24GB

DDS4   20GB/40GB

DDS5   36GB/72GB

DDS6   80/160GB

 

AIT Drives

AIT1   40Gb/100GB196_vxa-220external20drive

AIT2   80GB/200GB

AIT3   100GB/260GB

 

LTO/Ultrium Drives

LTO1   100GB/200GB

LTO2   200GB/400GB

LTO3   400Gb/800GB

LTO4   800Gb/1600GB

 

Tape drive compression (confusion)

 All tape drive manufacturers list 2 capacity figures in the specification of their tape drives, a lower capacity and a higher capacity. This is confusing and catches a lot of people out.

 

For example a DAT72 might imply it can backup 72GB of data to tape, but in the real world you could expect to see probably somewhere between 40-55GB of data being backed up.

Again a Ultrium 100GB/200GB might imply that you could backup 200GB of data onto tape, in the real world you might expect to see probably somewhere between 130GB to 160GB of data going to tape.

 

Why is this? It is important to remember that the reason 2 different capacity values are listed is due to the type of technology used in these modern tape drive’s hardware. The lower capacity value is generally the guaranteed capacity. The higher value can be misleading, but basically modern tape drives use compression. As data is transferred to tape, the tape drive hardware will compress data in order to use the tape media more efficiently.

 141_storageloader20lto20left

Different types of data can compress at different rates. I.e. databases can be compressed more efficiently than say pictures or mp3s.

 

The higher capacity rating is generally the total capacity of the tape drive assuming — it can compress all your data at a 2:1 ratio. We all live in the real world where we can have a range of different applications and data stored on our computer systems, in our experience the higher capacity has never been attained and you should not rely on the higher compressed capacity to backup all of your data.

 

 

Century IT Services – Getting IT Right
Providing Computer Support & Network Support to businesses in Hampshire, Dorset, Surrey, Wiltshire, Sussex & Berkshire