RAID question for a RAID noob

[Duke{CLR}]

I have a third HDD arriving soon. When I put my new MB in I play on loading the three drives in a RAID 5. Should I just plug all these in and try to install XP on the RAID or should install XP first then turn it into a RAID.

Any linkage to RAID tutorials would be greatly appreciated.

[Zantheus]

Check this link out bro it seems to answer a few different things...and by the sounds of it you set RAID up before OS...hope it helps

http://www.techimo.com/forum/t196824.html

[CHOPS123]

good luck buddy.....I hope you dont own a asus mobo......That good old f6 while installing os......blows. Let us know how it turns out. Just google raid problems on the Asus maximus......they are all over the place!!!

[paceman]

IF you want your OS on the RAID array, then the array must be created FIRST.

You could also put your OS on a single drive, and then everything else on the RAID array.

[paceman]

A brief reason.

The data (bits & bytes) get spread out over the 3 (or more) drives. A parity bit is also created. So if you lose a drive, then data can be recreated from the remaining data and the parity bit.

[mapes]

Correct you want to use your MB bios utils to create the raid which afflictively turns your three drives into one C: drive. then install the OS ontop of that.

[pigworthy]

Your new raid drive will be the size of 2 of the drives added together I believe also.

[paceman]

Your new raid drive will be the size of 2 of the drives added together I believe also.

Almost - in RAID 5 some space has to be used for the parity bits, and so you lose a little space. In RAID 0, 1, 10, and JBOD you get the total amount of space.

[Duke{CLR}]

So witht he 3 250 mb drives together I get about 500 mb of space?

[mapes]

Your new raid drive will be the size of 2 of the drives added together I believe also.

What pigworthy said is right. You lose 1/3 of total aggregated drive space to parity in a 3 drive raid 5.

This is correct. Since it's a three drive raid 5. When the system writes data to the stripe across the three drives it writes a block (A) of data to drive 1, then a block (B) of data to drive 2 and then parity to the third drive (A+B). Note it alternates between the drives. so parity is spread out over all three drives. so you have 1/3 of the space used by parity

Almost - in RAID 5 some space has to be used for the parity bits, and so you lose a little space. In RAID 0, 1, 10, and JBOD you get the total amount of space.

Your is wrong except for jbod...Which is usually used for striping unevenly sized disk drives.

Raid 1, 10 and 0+1

Raid 0 = stripe... capacity of both drives added together
Raid 1 = mirror... half the capacity of total drive space
Raid 10 and or Raid 0+1 is a combination of striping and mirroring. Minimum 4 drives need for each.

For example with 500GB drives

Raid 0+1

1st set of 2 drives striped=1TB, 2nd set of two drives striped=1TB, both stripe sets mirrored=1TB

Raid 10

1st set of 2 drives mirrored=500GB, 2nd set of 2 drives mirrored=500GB, both mirror sets striped=1TB

[paceman]

BAH - You're correct.

I wasn't specific enough. What I meant to say was you didn't lose any to parity. I sometimes forget to say things that are obvious to me, but not to people that are asking the questions.

[Duke{CLR}]

Thanks guys I am learning a lot.

Now lets say one of my drives fails. How would I know? Is there some software that runs to monitor all this?

[paceman]

Thanks guys I am learning a lot.

Now lets say one of my drives fails. How would I know? Is there some software that runs to monitor all this?

Depends on the hardware. I have a RAID card and it squeals like banshee if one of the drives fails.

The previous card I had would stop at boot up and display an error. No idea if it did anything if it failed while the system was running.

If it's on your MOBO, hopefully your manual will tell you.

[mapes]

Thanks guys I am learning a lot.

Now lets say one of my drives fails. How would I know? Is there some software that runs to monitor all this?

Depends on the hardware. I have a RAID card and it squeals like banshee if one of the drives fails.

The previous card I had would stop at boot up and display an error. No idea if it did anything if it failed while the system was running.

If it's on your MOBO, hopefully your manual will tell you.

Yep if a drive fails your MB should scream at you. Since you created the raid in hardware all of the monitoring should be in the BIOS or via a software Util from the MB manufacturer.

In a 3 drive RAID 5 you can survive a single catastrophic disk failure without data loss. Because parity is calculated by summing the data being written to the other drives. How this works is the magic of the parity. If you look at my earlier post on how data and parity is written you'll see that you can automatically recover data by using the parity on the other drives

Like this


Disk1
(data A written)

Disk2
(data B written)

Disk3
(Parity=sum of A+B)


So if you lose disk1 you can recreate disk1 by subtracting the surviving data from the parity i.e (A+B"Parity") - B = (A data set). You can recreate the parity by just recalculating from A and B again. Hope that makes sense.

Of course your screwed if you lose two drives.

[drunken_chef]

all of the motherboards I've set up came with utilities that monitored the health of the array.