If you've not heard of "RAID", let me enlighten you.
Basically one can operate a computer with more than one hard drive. A lot of people already have more than one hard drive, but this is usually because a new drive has been added to overcome a capacity problem... too many music files or pictures, and more capacity is needed to keep the computer running. Often, also, an old drive is left in place as a slave to provide some sort of backup... usually a BAD idea because an old drive can slow a fast system down to a crawl.
RAID was originally introduced, because at that time hard drives were not very big and the cost of a really BIG drive in days of old was horrendously expensive. The answer was to make an array of smaller, cheaper drives. RAID 0 is the name given to the method that uses the array by spreading data across the set of drives in such a way as to make the user believe he has just one large drive. This is called "striping" and, if anything, can dramatically reduce the reliability of a system. RAID 1 is completely different however. This does not increase system capacity one iota, in fact it hides from the user a full 50% of available hard drive capacity by establishing a mirror of the main operating drive on a second drive of (usually) equal capacity. There are also other newer varieties of RAID such as type "5" now as well, but the type I chose for my updated system is RAID 1, wanting data security not extra capacity. Reliability mathematics give a neutral increase in data reliability for a twin drive RAID 1 configuration , but as most failures these days are rarely "end of life", being usually "random" failures, more to do with poor manufacturing, software or design problems, I don't think the theoretical 50,000 hours MTBF is ever likely to be achieved.
RAID 1 lets me run my computer even if the main drive fails completely. At this point I would fit a replacement, and this would be automatically installed as a new mirror drive. Such is the design of a decent modern system, I could even remove the old drive and fit a new drive without turning off the computer, but this is more a feature of the design of the new serial hard drive interface and the physical design of hard drive power supply arrangements.
How does one go about the change to a new RAID 1 system, when one's existing system is running OK?
Unfortunately there is one vital requirement that must be satisfied before a RAID system is contemplated and that is the motherboard must have the necessary RAID chipset; if not you will either need to buy one with this feature, or maybe fit a plug-in RAID card. Considering the expense and work involved I would suggest a new motherboard as this is likely to result in a faster system. Why is this? A new SATA hard drive will have an interface which operates at a faster speed than that permitted by a typical PCI slot (into which you would plug your plug-in RAID card), although you can of course limit the hard drive speed by fitting a jumper. Not a good solution as potential doubling of speed is sacrificed.
I'll explain what I did. Bearing in mind that my hard drive carries a tremendous number of emails, huge numbers of music and picture files, masses of documents and spread sheets and the usual paraphernalia one would not like to lose, I initially made a clone of the hard drive using a proprietary program. If anything went wrong at least I would have a copy of everything.
The first step, having ascertained that the motherboard can handle RAID is to fit a second hard drive that is equal in capacity, or bigger than the existing drive. If your current drive is say 120Gbyes then fit a similar one or larger, say 160Gbytes. A word of warning... different manufacturers can have different hard drive geometries so that a 160G drive from one may have slightly more, or less, than that from another manufacturer. The second drive cannot be smaller, even by a few bytes than the original otherwise RAID conversion will not proceed. One way round this sort of problem is to use a proprietory partition manager to tweak the size of the original drives main partition to make it slightly smaller than the new drive.
Having fitted a second drive, on which a mirror of the original will be made by the RAID software, you will need to install RAID drivers and RAID software.
Copy the RAID drivers to a floppy disk. There will be advice on how to do this in your motherboard documentation or included on the motherboard driver CD. A floppy disk is not a mandatory requirement if your computer hasn't got a floppy drive but you do need an alternative. You can copy the drivers to a CD or you can copy them to a USB memory stick. I have a USB floppy drive so it was easier to use a floppy disk.
The second step is to install the RAID drivers in the computer. This has to be done in a special way. For Windows XP, for example, you will need the Windows XP system disk.
Arrange for the BIOS to select the CD drive as the boot drive and the hard drive in second place. While you're in the BIOS, also set the system to "RAID". The exact details for this vary with motherboard manufacturers and will also depend on whether you're using IDE or SATA hard drives. If you are successful, then during the boot-up phase you will see a screen that includes the state of your RAID system. This is liable to have red lettering and various warnings and error messages at this stage.
Hopefully the computer will boot from the Windows CD and here you need to be poised with one's finger above the F6 key as only a short period is given early in the boot phase when a message appears at the bottom of the screen about "proprietary drivers". Press the F6 key when the message appears. Nothing will actually happen at this stage, but later on you will be prompted to offer up your special drivers.
If all goes well there will be a pause in proceedings and the drivers will be discovered by the computer. A message will appear on the screen and you will need to select the particular driver that is right for your system (eg ICH8 or whatever...). After selecting the drivers for your specific motherboard chipset, proceed say to the "Repair" screen and if you wish you can perform a hard drive check using CHKDSK, or you can just type EXIT.
The procedure you've followed will have placed RAID drivers on your hard drive and you can proceed to the next phase. Without these RAID drivers the RAID software package cannot run properly.
At some convenient point remove the Windows CD and allow the computer to boot up normally.
Next you will need to install the RAID software. Mine was "Intel Matrix Storage Manager" which came as a utility on the motherboard driver CD. Just install this as you would any other applications software.
Opening "My Computer" in Windows XP will reveal two hard drives. Your old drive with all your data and the new drive soon to be used as the mirror. I would recommend partitioning and formatting the new drive at this point, then checking its capacity with the original drive to ensure the capacity is greater or equal to the old drive.
Opening the Intel software package will give you the status of your RAID system, initially showing error messages and the absence of any RAID hardware.
Open the "Actions" tab and select "Create RAID Volume from Existing Hard Drive" and follow the instructions. What follows, if you have correctly followed the procedure is a "Migration" phase. The mirror disk is removed from view and your main drive copied to it. The process takes quite a long time, depending on computer speed, hard drive access time and of course its size, but you can use your computer during the migration process.
This technique enables one to make a RAID 1 system from an existing single hard drive system.
A year or two later... February 2009
Eventually my pair of 250Gbyte drives got completely full. After lots of deleting of unwanted data and files for the umpteenth time there was nothing for it but to buy a couple of larger drives and fit these in place of the smaller ones.
This is where I learnt more about RAID1. I unplugged one of the two drives and fitted a new 500G drive. A Rebuild process got underway and soon I had a RAID 1 with a 250 and a 500g drive. Next I unplugged the remaining 250G drive and fitted the second 500G drive. After another period of rebuilding I had a pair of 500G drives.... or had I?
Strangely, when I looked at drive C it was still full. Only a few tens of Meg free space. Where was all the free space? Maybe a partition manager would find it and I can free it up?
But no.. I tried several makes of partition manager but none could see the missing space. What next?
The solution was fairly easy but not without concern. I decided to remove one of the two disks from the RAID volume (this is one of the options revealed by typing CTRL I during boot-up) and hopefully I would be able to see the extra space and increase the existing partition to maximum. The trouble was that a warning messge came up saying that I'd lose all my data if I dared delete the mirror drive from the RAID setup, so it was with tongue in cheek I went ahead. No need to worry, as when I looked at the newly discovered drive that showed up in "My Computer" it showed that all the data was still present (ie a mirror of Drive C). Partition Manager grabbed all the free space and I was rewarded with a 500Gbyte partition now only half full.
I then repeated the process and, despite dire warnings to the contrary, the computer booted up normally. all the data was still present. Partition manager reclaimed all the free space and now I had two half full 500G drives.
Next I went into Intel Matrix Storage Manager and elected to make a RAID 1 system from the existing hard drives. This proceeded as a "Migration" and I was able to use the computer whilst the migration went ahead (a total of 2 hours 40minutes to mirror 250G of data and 250G of free space).
I wonder when suppliers will add the extra procedure to their utilties as it must be a common requirement to want to increase the size of a RAID system?
Now, lets move forward 5 years to 2014.
By now I've supplied many new computers with RAID 1 systems.
I've also met problems, some a little odd, associated with these.
Once or twice the RAID system has gone wrong. In one case the system ran for ages without the owner being aware that one disk had fallen by the wayside. What's supposed to happen is somewhere in the BIOS a command is activated which copies data to the hidden disk of the pair. This is totally automatic and invisible to the owner. The second drive is hidden from view and might just as well not be there, except if the main drive stops working. At this point the main drive is hidden away and the mirrored copy takes over becoming "Drive C".
One reason the RAID breaks is if the special RAID command in the BIOS is turned off. This could happen in a number of ways.
If the CMOS battery fails and the BIOS settings are lost or corrupted or if the owner for some reason decides to alter the settings... I've had instances of "Failsafe Settings" being activated (RAID is not included in these) or if the hard drive settings or boot sequence is altered. Unfortunately it's not always easy to see what happened after the event and swapping the "failed" drive for a new mirror drive is the best solution.
My own computer has two sets of RAID 1 drives. One set is a pair of 1Tbyte drives operating through the BIOS. A second set of 2Tbyte drives is operated via Windows 7 software RAID 1.
The other day I noticed a warning sign, actually a message superimposed on the Intel Rapid Storage Technology icon. I looked around for a new hard drive but alas I didn't have one, so I went into the Intel Manager and selected "Rebuild". This was accepted and the rebuilding commenced. I rebooted and the BIOS RAID screen declared that rebuilding was taking place. This completed without a hiccup and the computer is now running normally.
What had caused the problem? I checked prior to rebuilding and the active drive was warm but the bad drive was cool to the touch. The only thing I'd done before the crash was to update Windows 7 with two "important updates".
These were KB2825635 and KB2553065 both reported as "successful" on 16th August although they are for Office 2010 which is not installed... odd. There were 12 updates made on the 14th August and 2 on the 15th. I rarely boot the computer so it could be any of these. We did have a mains failure last week. It lasted only a few minutes.. maybe it was that?
A note from 19th September 2014
Today I was using my computer with lots of things open PhotoShop, Outlook, PAF5, Excel and Google Chrome when suddenly everything went suddenly quiet. Yet another power cut. Always best to call Southern Electric as they're rarely aware of power cuts around here. We've lost our power I said. After lots of discussion and typing noises .. yes they knew about it and it'll be back on by 3pm. At 10:15am it came back on. My computer booted up with a Raid crash indicated on the hardware system controller and a Raid crash indicated on my software drives. Both started a repair but before they finished the power went off again. I rang a second time but within 5 minutes it came back on. The computer carried on its repair. At 4pm off it went again only to come back on ten minutes later. I rang again and demanded compensation. I now have an email address and a Job Number and intend to claim. By 6:30pm both Raid systems had finished their repairs and everything is fine. Without Raid the system would probably never started up. I made a note to buy a UPS when I return from holiday. Maybe I should charge it to Southern Electric?