RAID Presentation Raid is an acronym for “Redundant array of independent Drives”, or Redundant array of inexpensive drives”. The main concept of RAID is the ability to take multiple drivers and combine them together. Another type of RAID is RAID 5

How RAID works Raid is used to take multiple drives and have them virtualized as a single driver. All Raid structures contain one of two primary purposes: aggregated storage space or data redundancy. Both regular RAID and RAID 5 work the same way but what they can do is different.

How RAID 5 works Raid 5 provides a very redundant fault tolerance in addition to performance advantages allowing data to be safeguarded. Raid 5 requires at least 3 120gb hard drives, you will have 240gb of actual usable space. The more drives you use then the more efficient your storage space becomes. If you had five 120gb hard drives, you would have 480gb of usable space.

Data redundancy Your data can survive a complete failure of one hard drives, but if two drives fail at the same time, ALL data will be lost. Raid 5 array can actually still be used with one drive completely missing or not working. The data will then be rebuild on the fly. Recommended that you have a extra hard drive by your computer if this ever happens.

RAID 5 Raid 5 has a increased over head. This is the cost to the person for the extra hard drive that is taken up by the parity. If you have two hard drives and you want to have that much space available, you need to buy one more hard drive for parity.

Striping parity Data is “striped” across the hard drives, with a dedicated parity block for each stripe. A, B, C and D represent data “stripes”. Each stripe vary in size from 4kb to 256kb per stripe. Stripes with a subscript P are the parity blocks. The parity is responsible for the data fault tolerance and is also the reason why you lose the amount of space equivalent to one drive

Striping parity Lets say the second hard drive fails. When the new one is put in place the RAID controller would rebuild the data automatically. The data segments A1 and A3 would rebuild A2. Parity blocks are determined by using a logical comparison called XOR.

RAID performance Raid 5, stores one file in three different hard drives. It then can be accessed in 1/3 the time. Because it will be read from all three drives. Each hard drive stores 1/3 of the file. This in a perfect situation, causes your read speed to be tripled – with even more performance potential in RAID 5 arrays containing additional hard drives. THE downfall is there is an increased overhead when writing to the drives caused by parity calculations.

RAID 10 RAID has levels 0-9, but you can add two single digit numbers to create a 2 digit number like RAID 1+0 to get Raid 10. Raid 10’s advantages are its very fast, it’s crash proof, and it eats disk space.For Raid 10 you need at least 2 physical hard drives. You also need a disk controller that’s understands RAID. Raid 10 works by striping and mirroring your data across at least two disks. Mirroring, or RAID 1, means writing your data to two or more disks at the same time.

RAID 10 If one disk fails then completely, then the mirror preserves the information. Raid 0 is stripping which allows the data to be broken up and written to different hard drives. This improves the performance because the computer gets data from more than one disk at the same time. Raid 0 in not really a raid level because it doesn’t provide any redundancy to protect information. Its still considered a raid level.

Back up and Raid 1 Although the data is written on to two disks, the data is not being backed up. If your system fails, rather then the disk, suffer an error an enormous amount of data could be sent to both disks at the same time, which would corrupt both drives. If using RAID 1 then you should still have a back strategy in place, but putting raid 0 and raid 1 together and getting raid 10 secures the data better because mirroring duplicates all your data. It’s fast because data is striped across two or more disks at the same time.

Disadvantages of RAID 10 The disadvantages of having RAID 10 is that it cuts your effective disk space in half. Since all data is mirrored, two 60 GB disks give you a total system capacity of 60 GB. And you should use identical disks when creating a mirrored array. Raid 10 is also slightly more complex to set up than conventional storage. It usually takes about 10 minutes to install raid on your computer. If the disk controller on your mother board doesn’t support Raid 10 then you can get an add-in disk controller card.

History of raid David A. Patterson led a team at the university of California, Berkeley that developed the idea of RAID storage. In 1987 Patterson said “We had just been working on RISC processors, and we consciously said, Processors are going to start getting fast, improving faster than they have in the past”. Patterson then had the graduate students think about ideas that were involved with the processes of making Processors faster.

History of RAID 1956 – IBM officially announces the RAMAC 305, the first hard disk system, which holds 5MB of data – Ampex develops helical scanning video recording, which well later be adapted for high- capacity tape backup – IBM Advanced disk file used one head for each disk surface, which eliminates the need for compressed air to position heads – IBM’s hermetically sealed Winchester hard disks become the standard design for disk drives.

History of RAID 1979 – Philips demonstrates optical storage drive technology as part of a joint venture with control data corp – David A. Patterson leads a team that defines RAID standards for improved performance, reliability – EMC develops the concept of network- attached storage 1998 – Gigabit Ethernet becomes a formal IEEE standard.

History of raid Raid 5 was released in 1995, on June 8. Raid 0 was released on march 5, 2004 Raid 1 was released on June 5, 2007 Raid 10 was released on June 7, 2007

Different type of RAID RAID 6 RAID 53 RAID 5 RAID 0+1 RAID 4 RAID-s RAID 3 RAID 50 RAID 2 RAIDZ RAID 1 RAID 0 RAID 7 RAID 1+0

Manufactures Promise technology Inc 3ware inc Ciprico inc RAIDmax Arco Computer products, inc Bering technology inc, Chih Kang Material Co Casepro technology Co

Control cards $ PCI Express SATA / IDE combo controller card - $21.99 Areca ARC-12361ML-2G PCI- Express X8 SATA 2 controller Card - $ Highpoint Raocketraid 4310 PCI- Express x8 Four-port SATA and SAS hardware - $ Highpoint Raocketraid 2640X4 PCI-Express x4 Four-port SATA and SAS RAID - $99.99

References ory.aspx?SubCategory=410&Tpk=RAID %20cardshttp:// ory.aspx?SubCategory=410&Tpk=RAID %20cards /The_Story_So_Farhttp:// /The_Story_So_Far raid-5-really-works/ raid-5-really-works/