Solve : Difference between RAID 2, 3, and 4??

1.	Solve : Difference between RAID 2, 3, and 4??
Answer» Hello, good evening. I don't really understand the difference of these three RAIDs. I search it in the net but non of the links give the exact answer or direct answer of the differences of the three RAIDs. So I just post here just hoping if someone could enlighten me and explain it briefly the differences of 3 RAIDs. So, what's the difference between RAID 2, 3, and 4? Much better if there are examples. Thanks advance. Your question involves a complicated TOPIC and I believe not many forum members have significant expertise on that subject. But, I can't believe you can't find good info on this via an Internet search. I'll list two references I found: http://www.ecs.umass.edu/ece/koren/architecture/Raid/basicRAID.html http://www.acnc.com/raid.htmlQuote So, what's the difference between RAID 2, 3, and 4? RAID 2: The same as RAID 0, except it uses the data bits to stripe rather than data blocks. RAID 3: Also similar to 0, this one uses data bytes instead of blocks and has an extra drive dedicated to parity. RAID 4: Like 3, except it uses data blocks.Hello, good evening. When using RAID, is it necessary to use same hard disk size? For example: I have 80GB, do I have to PAIR it with 80Gb as well? OR I can just mix it with 160GB and so on?Quote from: SHENGTON on January 18, 2011, 09:48:09 AM I can just mix it with 160GB and so on? With Raid 0, 80 GB + 160 GB gives you a 160 GB array. With Raid 1, you would get an 80 GB array. http://en.wikipedia.org/wiki/Standard_RAID_levels Why are we doing his homework ? ? Your posts guys are very informative. It makes me easy to comprehend. Last two questions: 1. In RAID 2 and 3, if the parity disk is damage can I still recover the files? 2. In RAID 4, if the ECC disk is damage can I still recover the files? Quote from: PATIO on January 18, 2011, 04:52:22 PM Why are we doing his homework ? ? Indeed. Shengton, have you heard of Google? This is not an assignment.Do we assume you want to do RAID on Linux? Here is a book for about $10. http://www.amazon.com/Managing-RAID-Linux-Derek-Vadala/dp/1565927303Your posts guys are very informative. It makes me easy to comprehend. Last two questions: 1. In RAID 2 and 3, if the parity disk is damage can I still recover the files? 2. In RAID 4, if the ECC disk is damage can I still recover the files?Quote from: SHENGTON on January 20, 2011, 09:21:13 AM Your posts guys are very informative. It makes me easy to comprehend. Last two questions: 1. In RAID 2 and 3, if the parity disk is damage can I still recover the files? 2. In RAID 4, if the ECC disk is damage can I still recover the files? In all forms of RAID, the intent is to increase performance, speed, by having redundant data. At the same time, there is some measure of increase in RELIABILITY. Modern ATA type hard drives have very large capacities, often more that needed for most applications. The extra capacity is used in RAID to increase speed and reliability by use of extra capacity. Implicitly RAID is faster and more reliable than a simple basic Hard Drive type. The most frequent type of HDD failure is not the entire drive at once, instead a portion of the drive becomes unusable. So that recovery of the failure of an entire drive is not a principal concern in RAID. Raid allows the system to continue even when a significant amount of data becomes unreliable, thus reducing the down time of a server. However, recommended practice is to have weekly backups of the entire system, whether or not it is a RAID system. In a nutshell, RAID is not a way to avoid the need for backups. It improves speed and shortens down time of a service. Short answer, In many forms of RAID one entire drive may fail and the system will continue working at lower speed. {The above generalization ignores the fact that in a rare case a drive failure in a well designed RAID system has taken down thew entire system because of an ELECTRICAL failure in one drive that shorted out the power supply. Now some designs have redundant power supplies.}

Answer»

Hello, good evening.

I don't really understand the difference of these three RAIDs. I search it in the net but non of the links give the exact answer or direct answer of the differences of the three RAIDs. So I just post here just hoping if someone could enlighten me and explain it briefly the differences of 3 RAIDs.

So, what's the difference between RAID 2, 3, and 4?

Much better if there are examples.

Thanks advance. Your question involves a complicated TOPIC and I believe not many forum members have significant expertise on that subject. But, I can't believe you can't find good info on this via an Internet search. I'll list two references I found:

http://www.ecs.umass.edu/ece/koren/architecture/Raid/basicRAID.html

http://www.acnc.com/raid.htmlQuote

So, what's the difference between RAID 2, 3, and 4?

RAID 2:
The same as RAID 0, except it uses the data bits to stripe rather than data blocks.

RAID 3:
Also similar to 0, this one uses data bytes instead of blocks and has an extra drive dedicated to parity.

RAID 4:
Like 3, except it uses data blocks.Hello, good evening.

When using RAID, is it necessary to use same hard disk size?

For example: I have 80GB, do I have to PAIR it with 80Gb as well?

OR

I can just mix it with 160GB and so on?Quote from: SHENGTON on January 18, 2011, 09:48:09 AM

I can just mix it with 160GB and so on?

With Raid 0, 80 GB + 160 GB gives you a 160 GB array. With Raid 1, you would get an 80 GB array.

http://en.wikipedia.org/wiki/Standard_RAID_levels

Why are we doing his homework ? ?

Your posts guys are very informative. It makes me easy to comprehend.

Last two questions:
1. In RAID 2 and 3, if the parity disk is damage can I still recover the files?
2. In RAID 4, if the ECC disk is damage can I still recover the files? Quote from: PATIO on January 18, 2011, 04:52:22 PM

Why are we doing his homework ? ?

Indeed.

Shengton, have you heard of Google?
This is not an assignment.Do we assume you want to do RAID on Linux?
Here is a book for about $10.
http://www.amazon.com/Managing-RAID-Linux-Derek-Vadala/dp/1565927303Your posts guys are very informative. It makes me easy to comprehend.

Last two questions:
1. In RAID 2 and 3, if the parity disk is damage can I still recover the files?
2. In RAID 4, if the ECC disk is damage can I still recover the files?Quote from: SHENGTON on January 20, 2011, 09:21:13 AM

Your posts guys are very informative. It makes me easy to comprehend.
Last two questions:
1. In RAID 2 and 3, if the parity disk is damage can I still recover the files?
2. In RAID 4, if the ECC disk is damage can I still recover the files?

In all forms of RAID, the intent is to increase performance, speed, by having redundant data. At the same time, there is some measure of increase in RELIABILITY. Modern ATA type hard drives have very large capacities, often more that needed for most applications. The extra capacity is used in RAID to increase speed and reliability by use of extra capacity. Implicitly RAID is faster and more reliable than a simple basic Hard Drive type. The most frequent type of HDD failure is not the entire drive at once, instead a portion of the drive becomes unusable. So that recovery of the failure of an entire drive is not a principal concern in RAID. Raid allows the system to continue even when a significant amount of data becomes unreliable, thus reducing the down time of a server. However, recommended practice is to have weekly backups of the entire system, whether or not it is a RAID system.
In a nutshell, RAID is not a way to avoid the need for backups. It improves speed and shortens down time of a service.

Short answer, In many forms of RAID one entire drive may fail and the system will continue working at lower speed.

{The above generalization ignores the fact that in a rare case a drive failure in a well designed RAID system has taken down thew entire system because of an ELECTRICAL failure in one drive that shorted out the power supply. Now some designs have redundant power supplies.}

Solve : Difference between RAID 2, 3, and 4??

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