RAID on hard drives

I understand that when you have 2 hard drives you can use the "RAID strip 0" or "RAID stripe 1".

first of all i was wondering whats the difference between the two?

Second i was wondering if any one can tell me how to accomplish this feat?

The hard drives are going to be in a Dell Inspiron 1720 with windows vista home premium.

hard drive 1: 160GB @7200 rpm
hard drive 2: 200GB @7200 rpm

thanks guys, anyones input or information on the subject will be much appreciated!

 

Just cause your laptop has two harddrives in it, does not mean it supports Raid.
Your system cannot support a redundant array of independent drives.

Raid 0 means that part of each file is located on each drive, so you essentially double the speed of the drives, but it does not work very efficiently. If you have two 200gb 7200rpm drives, your system would see it as a 400gb 14,400rpm drive. But if one drive fails, you loose all of your data.

Raid 1, means that there is the same data on each drives.
So if you had 2 200Gb drives, you would have 200gb of space, with a 200gb backup. If one drive fails the second drive will still work, so you do not loose data.

Well your system cannot run a raid setup, so you do not have to worry about it.
Your system only supports spanning, meaning that you will have a local disk c of 200Gb and a local disk d of 160Gb.

K-TRON

 

A RAID 0 setup makes accessing and writing files faster, but is more dangerous as you will lose all your data if one of the disks fail. A RAID 1 setup is more for data integrity, as it mirrors the data on one HD to the other. Some performance increase can be noticed at times in RAID 1, but it is far less than RAID 0. If you want to learn more, read the Wiki article:
http://en.wikipedia.org/wiki/RAID

There are various ways to achieve RAID. Software RAID can be achieved by your Operating System or third party applications, but will take up some of your PC resources and might not work too well. Hosted RAID requires a RAID controller, which the Inspiron 1721 has, but the 1720 doesn't.

 

Do SSDs support RAID? They'd be fast as hell with RAID 0. xDD Is it possible to combine RAID 0 with RAID 1? Seems unlikely, but it would be nice to have two 10,000 RPM drives using RAID 0 backed up to a 7,200 RPM drive using RAID 1.

 

Yes, you can have raid 0 and raid 1, it is called RAID 5.
Raid works best with identical drives.

You should be able to put two SSD's in Raid.
I doubt anyone has done this, since they are so damn expensive.

K-TRON

 

K-TRON thanks for your input man, but i have another question are you saying that even if my system where capable of accepting RAID you would not advise it any how?

 

I use Raid 0 in my Voodoo laptop, I use it cause I would rather sacrifice the safety of my data for a nice performance boost.

I do not advise using raid, in a laptop, which uses software raid, It is only about 10-25% efficient.
I have hardware raid, which is about 50% efficient.
Hardware raid, means that their is a hardware controller, which runs the array, rather than a software program in the background.
If you have the ability to have raid, I would suggest raid 0 or raid 1. Its really up to the user.
Raid 0 is faster than Raid1, but your data is not as safe.

K-TRON

 

So if you could not tell i am fairly new to laptops and laptop performance!

If you would not mind could you tell me what it would take to have RAID, i understand that the 1720 does not come with what you referred to as a "RAID controller" however do the hard disks have to be the same type or whats the deal here? i guess what i am asking in short is what exactly is a "RAID controller" (i think i understand what it does, its what you said in your first reply!) ( i also understand that you can do this using software, but i dont want that.)

is their an after market RAID controller or does this depend on the types or brands of hard drives you are using.i know that is in round about language but i hope you get what i am trying to say!

 

A raid controller, is usually a VIA or a BROADCOM based Raid controller.
It is soldered directly to the motherboard.
This chip basically cuts the file in half, putting half of it on each of the drives.
Most laptops use software raid, my Voodoo is one of the few, which have hardware raid.

It is recommended to use identical disks for Raid, so that 1/2 of the data can be allocated in the same sector of the drive, as in the other one.
Ex: say you have a 4kb file.
2 Kb of the file is saved in sector 3215/25000 on the first harddrive.
the other 2Kb of the file is saved in sector 3215/25000 on the second harddrive.
if the drives are identical, the data can be shared in the same sector on each allocated drive.

Their are aftermarket raid controllers for desktops and servers, but not for laptops.

When I mention that their is software based raid, I mean that the bios has software, which emulates what a hardware based raid controller does.
You cannot download a raid controller, your bios would have to support it.

K-TRON

 

I gotchya, thanks for clearing it up for me too. i appreciate all the info you've provided.

 

Anytime, thats what we are here for.

K-TRON

 

I have bashed RAID 0 in two previous threads. But now want to say if you understand the risk and have a solid backup strategy in place for critical DATA. Then go for it as long as you understand. To K-T HW/SW did not know as I don't have RAID. So, many that say RAID have to be careful of? HW/SW? Correct, good to know. Thanks. K-T I am going to ask something a little off but not much. With one HDD two platters. You are writing file. Is it writing to both platters at the same time? Are the heads capable? Or one at a time?

 

damn, powerpack always asking questions on stuff I am not 100% sure on
hmmm,
Well this is a educated guess
Lets talk about a 2.5" mobile drive with two platters, and 4 heads, (one for each side of the platter)

Now, at any given time, the harddrive actuator can move the heads, so that all 4 heads are in the same spot on each of the sides of each platter at any given time. SInce 4 sectors can be touched by the heads simultaneously, the drive can read/write to all four sectors at the same time.
How the harddrive heads can distinguish and figure out where to put each data bit is beyond me. Harddrive companies will not release how this is done.
I would assume that all 4 sectors can be written to simultaneously, but its a gray area.
I am looking at the inside of my old 2.5" harddrive to figure it out.



Based on the ribbon cable around the actuator arm, we can see that there are two large wires on the top of the cable, eight thinner wires (probably cant see in the picture), and two larger wires at the base of the ribbon cable.
If you look at the underside of a harddrive head, you can see that 4 wires run to each head. I have no idea what these wires do, but they run to a small malleable surface which touches the surface of the disk (this is the known as the harddrive head)
Here is an image, (I am sorry if its not super clear, the image sensor on my Samsung NV camera is having problems distinguishing colors since the disk is so reflective)


It looks like the larger wires are used to power the electromagnets, which control the harddrive actuators movements.
The eight smaller wires, look like they control the data flow to each head.
The drive I have in the pictures is a single disk with 2 heads.
4 of the wires go to each head.
Routing from these wires and then going back to the small electronics in the harddrive, it looks like the eight small wires are controlled by two different circuits.
This means that each head can write/read simultaneously.
I assume that in a drive with four heads, there are 16 small wires, with 4 different controller circuits.

So to answer your question, yes all of the heads can be read/written to at the same time.



As far as raid goes, hardware raid is more secure than software raid. This is because a physical chip separates the data, not software. A physical raid controller is much faster and efficient than one which is based off of software.

As far as I know, the only laptops which have hardware raid controllers are my D900K based system, and the D900T based laptop. I am not sure what the D900C uses. It uses Intel raid, but based on the hdtune raid results from the d900c I have seen, the d900C uses a software raid controller, since its benchmark speeds are significantly slower than on my system.
Both the D900K and D900T use a VIA hardware Raid controller.

K-TRON

 

How can you tell if your BIOS supports raid? Does raid only work for SATA hard drives?

 

If your Bios takes 30 seconds to boot, then you have a system which supports raid.
Right after the bios loads, a black screen comes up for about 1 second, and then the raid manager appears.
It takes about 20 seconds for the raid manager to check if your raid array is healthy.
If its not healthy, it will not boot the raid array.
Also, you will have raid options in the bios.
As of now, only the d900 series, the Gateway P-6831FX laptop, the xps 1721 and the xps 1730 have raid capabilities. I am not sure if the toshiba x205 has raid.

If your laptop has two harddrives, but no raid support, this is called spanning mode. You have two separate drives in the my computer folder, one for each harddrive.

Raid can be done with both IDE and SATA harddrives.

In desktops, this can also be done with SCSI, Serial Attached Sexy, and Fibre Channel drives.

K-TRON

 

Youll know when you have a hardware raid controller, you will see it on startup.

My desktop takes like 5seconds for the RAID screen to go away even though i dont have a RAID setup

 

Thanks K-Tron and flipfire, very helpful. Guess I'll experiment with spanning my hard drives when I get time to do so.

 

Youre welcome,

Wow, I have no idea what happened to that first image, its all screwed up at the bottom. I guess I shut the camera off before the camera finished saving the picture to the card.

K-TRON

 

K-T we will talk and I will either walk away small or we will be better able to explain what is going on!

 

Not correct.

RAID-5 is a distributed parity system with N drives, you get N-1 capacity.

Raid 0+1 is striped mirrors, you have two stripe sets mirrored to one another.
They are completely different animals.

If we consider this from a usable space perspective, with a single drive being 1 then we have:
RAID-0 still equals 1 but has no redundancy
RAID-1 is .5 but has redundancy
RAID 0+1 (see above) is still .5
RAID-5 is (n -1) / n where N is the number of drives in the array

There are also double parity RAID-5 (some call it raid 51) which is used predominately by the big storage vendors (i.e. NetApps and EMC).

Anything other than identical drives is looking for trouble. It can be done, but is not a good practice.

A RAID controller would have no idea the drives are SS based. So yes.

Les (nee Flamenco) has done this and posted the numbers. They were astounding for RAID-0.

 

Okay, I may have gotten the Raid 0 + Raid 1 part wrong.
I am sorry. I read a book on raid a few years ago, and I really thought that it mentioned raid 5, as Raid 0 + Raid 1.
I will have to check the book and edit my post, if I am wrong.

K-TRON

 

K-Tron:

I've read numerous titles on the topic, including the UCB paper outlining RAID.

You aren't right.

 

OK? But nice link says nothing?

 

powerpack:

You have to download the PDF at the top of the page. I first read this.. well, let's just say more years ago than I would like to say.

 

I agree I didn't click the link but can you summarize at all?

 

RAID 0 - Uses two disks as a single one. Files (or parts of files) can be found on each and every disk. Decent performance increase for reads and writes, but at a huge cost as if one drive fails you loose everything. So technically the risk is twice as great as having a single drive. AFAIK, if you RAID 160GB and 200GB...you'll wind up with a 320GB "dual" drive (as I think the other 40GB might not be available as most RAID controllers need identically sized drives).

RAID 1 - Uses two disks in parellel, and each drive is a perfect copy of the other. One drive is always used for reads/writes, with the secondary drive being access to enhance file access speed if possible. Some performance improvement compared to one hard drive, but not as much as RAID 0. However, you would have to have both discs fail to loose data as opposed to RAID 0 needed only a single failure. Your final hard drive size is equal to the smallest drive in the set (so 160GB in your case).

RAID 5 - Requires a minimum of three hard drives. Two drives are used much like RAID 0, and the third drive is used to store a parity of the two drives's bits of information. Read performance is about the same as RAID 1, but write performance is worse than either form of RAID because of the XOR calculation needed for the third drive's data. Can survive any one drive failure with data being safe, but if two fail than all the data is lost. Best for those needing high capacity with data protection, but a limited number of available hard drive spaces in the PC. Final drive size = (n-1) * s...there n is the total number of drives and s being the size of the smallest drive.

There are other forms of RAID, but laptops do not support that many hard drives.

More info I forgot about:
Hardware RAID requires a controller built into the chipset of the motherboard, and I think the most recent Intel chipset is the ICH9 R (most laptops use the ICH8 or ICH9 and those do not support RAID). If you do not have an "R" chipset, you cannot ever add in hardware RAID support.

Software RAID is possible, but it really is not worth it as the performance penalties are HUGE.

 

RAID-5 is distributed parity; not dedicated parity. What you described is RAID-3.

A properly performing hardware RAID does not have a performance penalty for writes, a software raid may or may not depending on the implementation.

Try RAIDZ on Solaris 10u1 or later and talk to me about the huge performance penalites after that

Cheers,

 

Okay, lets see, I took a picture of the page in my book, and who is right?
Oh, thats right, neither of us.
I simply made a mistake and confused Raid 5 with Raid 10.
Raid 10 is the same as Raid 0 + Raid 1.
This is my handbook to computers: (the book which got me interested)

Here is a chart on Raid systems:


As you can see, my brain is a bit overloaded, and I simply mistaken Raid 5 and Raid 10.
I am sorry that I stated the wrong raid type. I did read the book 3 years ago. Give me a break.

This book is at my house, I am up at college, so I couldnt view it last night.
I had my younger brother take a picture of the chart for me to post here.

K-TRON

 

More pictures of textbooks lol. Hope this helps.

 

Man...I just found this and am dying to read it. Favs it will be until I can get to it. Im in Quebec presently with family for a graduation ceremony and my wife still grumbling because I brought my laptop lol!

Im finding myself more and more out of the loop with things like this and ssds. Ive had a company asking if I would be interested in testing there 1.8" 128Gb ssd (still working on this Greg) and also its been asked if I had a desktop to start testing new desktop ssds in regular and RAID mode. Companies are very aware of the dominance of desktops and the multi-uses for RAID configs.

In fact, watch out for Dell who are jumping into the RAID configuration options and testing on this daily.

Prob for me is right now my hobby (no profit) needs to expand so I can get a sufficient laptop for 1.8 testing as well as a desktop for the larger ssds. Anyone have any idea on how I can gt companies to pitch in here?

LOL!!! I am dying to get my hands on a MacAir to throw in a Mtron soon to be released 128Gb 1.8 ssd with read/writes at over 100MB/s. Woot!

"Jenny, I am not a smart man" - My buddy Forrest, Forrest Gump.

 

Les, just growl back! Kidding! And if you need me to take that trip let me know I can free up my schedule!

 

Excuse me.

I was completely correct.

Because Raid with dual distributed parity is not part of the standard, it is referred to as RAID5+1, RAID5DP (Double Parity), RAID6 and others depending on which vendor you're talking about.

As you can see, my brain is a bit overloaded, and I simply mistaken Raid 5 and Raid 10.
I am sorry that I stated the wrong raid type. I did read the book 3 years ago. Give me a break.[/quote]

No, I can't see -- I know that you were factually incorrect and you were corrected.

Do you argue test scores with professors in this fashion as well?

I don't need the chart or the pictures of the chart. I deal with this on a daily basis.

It's one thing to read about technology in a book and another to make a living from it.

 

Seems crazy to not have the adapters available as the desktop standard is still 3.5" form factor. This would allow for less products from a manufacturing point of view which is a good thing.

We're looking into SSDs for our fastest tier of big storage. Currently, it's 15K, 10K and 7200 (SATA). The 128GB size isn't radically different from our 147 GB 15K storage and for DB work it would literally scream. Even with the low average seeks of ~4 msec you're talking ~40x faster for SSD. Of course we have to get someone to pay for it too Then again, we also have to have the vendor certify 'em for safety's sake.

Become a consultant

Spec'd anyway. Let's see the benchmark results before we get too excited.

128GB is still going to be a little more coin than I can justify, but if they have a 64GB at a significant cost reduction I can probably swing that.

See previous

 

John, would you believe you were the second within a 12 hour span to use the words, "Become a consultant". I have a very close contact in Dell who works in Executive Support who stated much the same after I approached him for assistance as I was approached to help a company find a Distributor in Canada. He had stated that, if in my shoes, this hobby would have translated long ago and I was nuts not to grab a finders some of the stuff I have done.

At times, I wish I was a bit more business savy in this area.

 

Oh absolutely -- you know the subject matter quite well and that goes a long way.

Consulting? You and me both. I've only done a few consulting gigs and they came to me not the other way around. It's finding the next gigs that worry me, i.e. lining up extended business to keep the income stream intact

I could make more money consulting but at greater risk.

 

I know that this has nothing to do with the RAID on hard drives but....

and Les you dont know this but people like you and K-Tron (there are several others, but i have used your guy's *FREE* information the most!) and i thank you, but this is why i stick around this forum!

another thing is and if you dont mind me asking, what is your non-profit hobby?

 

I am honored, that we are able to help so much,
that is the best part about this forum, is that its a great source of information.

My hobbies are:
working on engines, building computers, making models of buildings for architecture class, building and inventing, pretty much anything where I can use my hands to build things.
I own a landscaping business, I have A1 computer certification, I am a certified diesel mechanic, and I drive a peterbilt and a homemade scooter.
I also enjoy helping others on forums, cause it makes me feel good.

K-TRON

 

John Kotches, Think, you drilled K-T hard! Not that some of what was mentioned. K-T might be wrong. Be nice it helps in discussions, I value your input.

 

Yes, powerpack, he did.
I must have misread what he mentioned, cause the way I read it and interpreted, I thought both of us had been wrong.
I am sorry John, you definitely have more hands on experience with raid than I do. I will have to do more research, so that I will better understand the more complex levels of raid.
+1 for you John, for helping to clear up my understandings of Raid

K-TRON

 

I will be the first to concede I do not have that much "hands-on" with RAID which brings me to my non-profit hobby ChevyTrucks which, for the most part, is assisting companies and consumers with ssd technology.

My RAID 'beginning' will come from many of you.

 

When you say you lose your data if a drive 'fails', are you meaning it goes kaboom as in it just has a random glitch and breaks, or is there some kind of possible 'fail' with a raid set-up?

What are the chances of a drive failing?

 

No the drive doesnt go kaboom.
Basically a Raid array fails when one of the harddrives just dies. The rate at which harddrives die is pretty slim, but when you have two or more harddrives, the probabilities that one of the drives fail doubles, triples, etc.
I have had blue screens on my system with a raid 0 array, and never had any problems. If you delete a crucial driver or part of the operating system, you could cause the operating system to fail, resulting in a NTLDR error, and thus no operating system.
With a Raid 1 array, when one drive dies, the other one will still chug along and keep all of your data. However on a raid 0 array, half of the data is on each drive, so if one drive fails, then all of the data is lost.

K-TRON

 

Okay. I'm thinking of installing a raid 0, it doesn't seem too likely that anything would fail in the near future.

 

I have raid 0 on my desktop computer and it hasnt failed yet and ive had it for over 4 years now! 'knock on wood'

 

Hi , How do i know if my laptop has raid controller
i have the toshiba quosmio G40 11D

 

Kabesss, please do not revive old threads.
Your Qosmio does support two harddrives but to my recollection it only supports two drives running in spanning mode. AKA. Each drive is recognized separately on their own SATA channel.
You can check to see if you have raid.
When the system turns on press F2 or Delete to enter the Bios.
If your laptop supported raid, you would see raid options in the main bios.
If you had raid, their would be a raid manager appear every time the system booted. If you do not see this, your system does not support Raid.

K-TRON