RAID is a method of combining n (when 'n' is any reasonable number >1) separate but similar (preferably identical) discs (of the same size) to appear as one to the operating system.
RAID 0 is where the discs are all used fully, but the information written to them by the OS is split into small chunks and the chunks are spread across all the discs to be written at the same time, meaning you have n discs writing the info at the same time, making it (theoretically) n times faster than a single disk.
This is great for boosting speeds when n>3, but I've got a RAID 0 array of just 2 WD 320Gb drives with 16mb cache each, and I've only noticed a 10% speed increase in sustained transfer rate, if that.
RAID 1 means that all the files you are writing to a disk are written to all the disks, meaning that each disk is an exact copy of the others.
(A more detailed article, including more types of RAID (beyond 0 and 1) is available on Wikipedia: http://en.wikipedia.org/wiki/RAID)
Pros and cons:
RAID 0:
Pro: This provides both increased write speeds and increased read speeds, because more disks are writing and reading at a time.
Pro: You get the amount of storage space that you expect from n number of drives.
Con: You're more likely to experience disk failure. Why? Well, if the MTFB (mean time before failure) of a single drive is 1,000,000 hours, then statistically if you've got two drives the chances of one failing in that time double, so the MTFB for the raid set becomes 500,000 hours. If you've got 4, then it's 250,000 hours.)
Con: In this type of RAID array, if one disk fails then the information on all of them becomes useless, as there is no duplication in any of the other disks and the information is split into small packets which make no sense when read on their own.
RAID 1:
Pro: Raises read speed slightly - if an intelligent controller is available, it will use each disk to read a different part of the information required, speeding up the read process somewhat.
Pro: Duplicates all data - this is the cheapest RAID method of backing up useful data - it extends the MTBF considerably.
Con: Does not raise write speed in the slightest, and will only transfer as fast as the slowest drive (or risk getting in a muddle).
Con: You're paying for extra drives without increasing capacity at all, so can be expensive if more than one extra drive is used.
Con: Although you keep your data in the event of any number of drive failures up to (n-1), usually a drive failure indicates that ALL the drives in the array are approaching end-of-life. As such, a single drive failure would theoretically oblige the owner to replace the entire array, not just one disk.
RAID 0 and 1 have more recently been overtaken with other examples that off a compromise between these extremes. RAID 0+1 was the first attempt, RAID 5 performs a similar function to that.
Implementing RAID:
Three methods:
Motherboard / Onboard: If your motherboard supports RAID, then you plug your drives in, pop into the BIOS and tell it to RAID 'em. This is bootable RAID, which means that you can install your operating system on the array as if it's a single drive.
Add in card: Since my motherboard didn't support RAID, I got myself a cheap (£5) PCI-E RAID 0 and RAID 1 Silimage Card. This does provide RAID (bootable RAID at that), but all the processing is performed by the CPU so it's not the best option. RAID controllers are better, but these will usually set you back more than £150.
Software RAID: This is the cheapest, and in most people's opinion, the worst. Software RAID is at best implemented by the OS, and sometimes even by 3rd party software running in the OS. This is non-bootable (since the OS has to have loaded for it to access the drives), and usually the slowest (seeing as the program is accessing CPU recources in the same queue as that game of runecape you might be playing.)
Oh yeah, you won't be able to run RAID on a single drive (obviously), so if you really feel you need it - trust me, and don't bother with RAID 0 unless you have good reason to - or can afford to slosh the dosh on RAID 5 or higher, you'll need to get either a few more WD 1Tb 64mb HDDs or (if you're stupendously rich and want some serious bragging rights) get 4 Intel X25-E 64Gb SSDs and put them in RAID 0, for your operating system and games. Stick the rest of your files on the WD. And after you've done that, send 4 more to me please
PS. Good guide. SATA-6Gbps soon/now too.
RAID 0 is where the discs are all used fully, but the information written to them by the OS is split into small chunks and the chunks are spread across all the discs to be written at the same time, meaning you have n discs writing the info at the same time, making it (theoretically) n times faster than a single disk.
This is great for boosting speeds when n>3, but I've got a RAID 0 array of just 2 WD 320Gb drives with 16mb cache each, and I've only noticed a 10% speed increase in sustained transfer rate, if that.
RAID 1 means that all the files you are writing to a disk are written to all the disks, meaning that each disk is an exact copy of the others.
(A more detailed article, including more types of RAID (beyond 0 and 1) is available on Wikipedia: http://en.wikipedia.org/wiki/RAID)
Pros and cons:
RAID 0:
Pro: This provides both increased write speeds and increased read speeds, because more disks are writing and reading at a time.
Pro: You get the amount of storage space that you expect from n number of drives.
Con: You're more likely to experience disk failure. Why? Well, if the MTFB (mean time before failure) of a single drive is 1,000,000 hours, then statistically if you've got two drives the chances of one failing in that time double, so the MTFB for the raid set becomes 500,000 hours. If you've got 4, then it's 250,000 hours.)
Con: In this type of RAID array, if one disk fails then the information on all of them becomes useless, as there is no duplication in any of the other disks and the information is split into small packets which make no sense when read on their own.
RAID 1:
Pro: Raises read speed slightly - if an intelligent controller is available, it will use each disk to read a different part of the information required, speeding up the read process somewhat.
Pro: Duplicates all data - this is the cheapest RAID method of backing up useful data - it extends the MTBF considerably.
Con: Does not raise write speed in the slightest, and will only transfer as fast as the slowest drive (or risk getting in a muddle).
Con: You're paying for extra drives without increasing capacity at all, so can be expensive if more than one extra drive is used.
Con: Although you keep your data in the event of any number of drive failures up to (n-1), usually a drive failure indicates that ALL the drives in the array are approaching end-of-life. As such, a single drive failure would theoretically oblige the owner to replace the entire array, not just one disk.
RAID 0 and 1 have more recently been overtaken with other examples that off a compromise between these extremes. RAID 0+1 was the first attempt, RAID 5 performs a similar function to that.
Implementing RAID:
Three methods:
Motherboard / Onboard: If your motherboard supports RAID, then you plug your drives in, pop into the BIOS and tell it to RAID 'em. This is bootable RAID, which means that you can install your operating system on the array as if it's a single drive.
Add in card: Since my motherboard didn't support RAID, I got myself a cheap (£5) PCI-E RAID 0 and RAID 1 Silimage Card. This does provide RAID (bootable RAID at that), but all the processing is performed by the CPU so it's not the best option. RAID controllers are better, but these will usually set you back more than £150.
Software RAID: This is the cheapest, and in most people's opinion, the worst. Software RAID is at best implemented by the OS, and sometimes even by 3rd party software running in the OS. This is non-bootable (since the OS has to have loaded for it to access the drives), and usually the slowest (seeing as the program is accessing CPU recources in the same queue as that game of runecape you might be playing.)
Oh yeah, you won't be able to run RAID on a single drive (obviously), so if you really feel you need it - trust me, and don't bother with RAID 0 unless you have good reason to - or can afford to slosh the dosh on RAID 5 or higher, you'll need to get either a few more WD 1Tb 64mb HDDs or (if you're stupendously rich and want some serious bragging rights) get 4 Intel X25-E 64Gb SSDs and put them in RAID 0, for your operating system and games. Stick the rest of your files on the WD. And after you've done that, send 4 more to me please
PS. Good guide. SATA-6Gbps soon/now too.
