Computer Hardware Blog

Like anything else it depends who you talk to.

Raid hard drive systems had their acronym explained as “Redundant Array of Individual Drives “and “Redundant Array of Inexpensive Drives”. The acronym for this is the shortened term “RAID”.

Capacity, reliability and performance are all important for file servers or other computer systems when you are storing large or very important files.

It is often said that “It is not if you hard drive will fail. It is at what point in time your hard drive will fail”.

Of course if your hard drives fail even if you have backup the last bit of data which was being written onto the hard drive when the failure occurred will be lost.

You can get much greater capacities, avoid losing data from disk failure, and do all this with the RAID (the acronym for the system).

RAID can now be done with standard commercially available hard drives so the cost is now within your price range for all the benefits and peace of mind RAID will give you.

RAID can be simply explained as putting the hard drives in parallel sequence.

The host adapter (usually called the RAID system controller) sits between one higher stream (on the computer side) and several lower rate data streams (on the hard drive side). When the computer writes to the disks , the host adapter takes high stream data and breaks it into many synchronized streams , one for each of the disks in process called “Striping “. Upon reading the data the host adapter takes the data stream from each disk multiplexes the sets of data streams and coordinates sending the resulting combined set of data onto the computer.

It is all a matter of redundancy which makes RAID such a good thing in most cases.

There are six different levels of RAID functionality depending on your requirements. – the level of data security and integrity you want as well as the size of hard drive space you want.

First of RAID Level 0 which spreads the data across multiple disks. You can get a similar effect to the RAID Level 0 by having multiple disks and using the features in Windows 2000 or its successor Windows XP.

Since the data volume and rate to any specific disk is a fraction of the aggregate you will receive larger capacity and better performance from a RAID 0 setup than from any one conventional disk.

As well data can be sourced from multiple drives as once. This can be most useful in shared situations which may benefit from enhancements in speed, two examples which come to mind are game servers and peer to peer (P2P) file or music file sharing servers.

However since there is no allocation for error correction or redundancy RAID 0 is not a safe system for vital data. Data will be lost on disk failure. Only use RAID 0 in situations where you need the extended disk capacity or performance gain but not enhanced data reliability.

Secondly in sequence there is RAID Level 1.

In the same way that RAID 0 focuses solely on storage capacity and performance with no concern whatsoever on reliable data storage RAID 1, which us also called “Disk Mirroring” uses disks in pairs to save the files in a redundant manner.

Several points.
One performance may be slower as it takes time for the host adapter to send the data and for the drives to write it to disk,
Secondly a user may delete or damage files which of course will be stored in that way on both drives.

Raid 1 hence offers better reliability than RAID 0 or the conventional drive setups but does not give full security for your data or enhanced performance.

Next in sequence we have RAID Levels 2, 3 and 4.

Raid 2 adds one or more disks to hold error correction codes with which lost data can be reconstructed.

Raid Level 3 is the same as RAID Level 2 but uses a simpler code the maximum storage capacity with Raid 3 may be somewhat less.

Raid Level 4 is nearly the same as RAID LEVEL 3 but instead of “Striping “ across disks is operates at a sector level, You now have the better situation of both a simpler , less intensive demanding system and as well as good data reliability . In addition performance may be enhanced as large data blocks can be written faster due to more coordinated writing to the drives in smaller “sector” areas.

Lastly is RAID Level 5.

Raid level 5 is the same as the excellent RAID Level 4 except that instead of dedicating a single disk to storing the data the data stream is striped across all the disks. You have greater performance with greater reliability for your computer systems.

A RAID setup may take some effort and training on your part.

Base your planning for your new RAID system on a careful analysis of your needs.

What is important in your situation currently? Disk size capacities, data reliability and integrity, performance or a combination or all.
Arthur Fellon
IT Consultant
Interest in Vintage Computing artfellon@yahoo.com
www.vintagecomputermanuals.com
www.badgerlinux.net

Fujitsu Limited, a leading producer of various electronics, announced this week the world’s highest capacity hard disk drive (HDD) for notebooks and consumer electronics, which exceeds capacity of previous-generation solutions by 25%.

Fujitsu’s new 2.5” MHY2 BH-series hard drives provide up to 250GB of storage space, which is 50GB more compared to industry’s top 200GB drives for mobile computers and consumer electronics. The novelty sports Serial ATA interface, uses 5400rpm motor and features 8MB of cache, which all should ensure performance comparable to typical mobile hard drives in 2.5” form-factor.

The manufacturer plans to make the new MHY2 BH family hard disk drives available in 40GB, 60GB, 80GB, 100GB, 120GB, 160GB, 200GB and 250GB capacities in the third quarter of calendar 2007. The new hard drives use perpendicular magnetic recording to provide record capacities.

The new hard drives are positioned for various laptops and consumer electronics with 200GB and 250GB models likely to find themselves inside devices of multimedia enthusiasts seeking for maximum storage space even while on the go.

With the advances of computer technology, hard disk failure is still a pulsating reality. And when hard drive failure occurs, hard drive recovery is not far behind. A hard drive is a collection of spinning aluminum discs which spin at 120 times per second. The discs surfaces are quickly spinning magnets. Hard drive is divided into sectors. Each sector, considered as the smallest physical storage on a disc, is 512 bytes in size. For files more than one sector, the file system has to allocate multiple files.

Small interferences to the spinning platter while in usage can damage the disc in one area. When some areas fail, the hard drive is relatively useless. This is where hard disk recovery comes in.

Hard drive recovery may be difficult. Oftentimes, it is an expensive and lengthy process. But recovery is not impossible. Fortunately, there are some procedures one can do before engaging a hard drive retrieval service.

If your computer makes ill-sounding noises then back up data as quickly as possible then purchase and install a new hard disk to facilitate hard drive recovery. More often than not, the cause of hard disk failure is corrupt Master Boot Record ‘MBR’, whose main function is to tell the computer how big the disk is. Corrupt MBR results in non-booting drive. Windows has easy to use tools that can address this problem. For DOS/3.1/95/98/ME, one can use SCANDISK. NT/XP systems use CHKDSK. Hard disk error may also be apparent in the initial POST or BIOS startup screen. The following factors could cause the problem: check the CMOS battery, reconnect IDE/SATA cables and Power cable, change IDE channel, swap the IDE Cable and check jumpers.

The following solutions to hard disk recovery are also suggested as a last option if you dont want to resort to expensive recovery service. These suggestions may sound a bit outdated but they work just the same.

1. Remove the hard disk cage and tap with the knuckle the outside casing. The shock may free any stuck mechanisms.

2. Place the hard disk upside down in the drive cage. The change in head geometry can occasionally solve the problem.

3. Putting the disk in a waterproof bag then put in the freezer overnight and back to the pc. This method might work and allow you to quickly transfer the data before it dies again. The theory behind is that the freezing could expand/contract metal components thereby freeing mechanisms.

If the data you lost is very important and cannot be retrieved using the above-mentioned methods then it is best to use hard drive recovery software or a recovery service before the problem gets any worse.