HDD - RAID - multiple issues - urgent attention

[sunandoghosh]

Respected nerds, techs, geeks and dear fellow members

I am having presently one hard disk drive seagate of 80 GB...

I am about to buy a hard disk tommorow....

In this contect can anyone plz clarify my following doubts...

A. I have heard that we can set up two HDD with RAID connection for striping and mirroring (I dont know what these means)...

((a)) Do i need to buy the second hard disk also of size 80 GB so that i can set up RAID connection with my previous hard disk of 80 GB...???

Or is it that i can purchase 200 GB (say) of HDD tommorow and with my previous 80 GB...I can still set up RAID Connection...????????

I mean is it mandatory that both HDDs be of same size for setting up RAID connection...????

() Also to set up RAID connection is it necessary that both hard disk should be from same company....?????

Or can i have say one seagate HDD set up with say another samsung HDD in RAID...?????

((c)) Can we have three hard disk drives and still set RAID connection....????

Or is it only restricted to two HDD...????

() what exactly is RAID connection and what benefits it offers....?????????

((e)) Can i still create drive image of my hard disk after setting up RAID connection......????????????????

Now as my computer and technical knowledge is very very limited (as i am a hardcore finance guy), my best and only recourse are wonderful forums like the one where i am posting right now. Its really great to have advice and suggestion of knowledgeable people here who do not have any self interest and are very helping in nature. So again I am daring to ask a few queries (infact more than few) and again hope that u people will really really help me out as u have always helped me in the past.

Thanks from deepest core of my heart for taking so much time effort and patience in READING and possibly replying...Its truly really and geniuenly appreciated....

And yes if anyone would like to add anything or say something else or suggest something better which i may be missing plz feel free to do so...

best regards

sunando

sunandoghosh at rediffmail dot com


sunandoghosh@rediffmail.com

 

[fishmahn]

Start with definition of RAID: Redundant Array of Inexpensive Drives (or Disks) (the 'I' part is sometimes called Independent, but I'm pretty sure it was originally Inexpensive) You take 2 or more disks, and combine them logically so the operating system sees them as a single drive.

Raid 0: Striping. Data is written to 2 or more disks alternating - piece one to disk 1, piece 2 to disk 2, etc. No data security, just performance improvement and no loss of space (i.e. 2 80gig drives = 160gig)

Raid 1: Mirroring. Data is written to both disks in duplicate - if one goes down, nothing is lost because there's a copy on the other (you can think of it as automatic imaging). No performance improvement (debatable), just redundancy and space 'loss' (i.e. 2 80gig drives = 80g).

(There's raid 2, 3, 4, but no one uses them any more that I know of)

Raid 5: Striping with Parity. Data is written to at least 3 disks. One disk is reserved for parity so if any 1 drive goes down, the data is still accessible. Redundancy with some performance improvement and reduced space loss (i.e. 3 80gig drives = 160g).

(there's more details like Raid 0+1, 10, etc. which are morphs or multiples of the above 3)

You don't HAVE to have the same size drives, but in most cases the excess capacity of the larger drive will be lost (i.e. an 80 & 120 in RAID1 gives you 80, in RAID0 you get 160). With the right controller in RAID0 you can have mismatched sized drives and not lose any (you'd get 200 per above example).

You don't HAVE to have the same mfg of drives, but because an 80gig from Seagate is a slightly different size than an 80gig from Maxtor, it's best.

For the other question that the above doesn't directly answer, (e) yes, you can still image.

Mike.

<font color=blue>Outside of a dog, a book is man's best friend. Inside the dog its too dark to read.
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[sjonnie]

<i>>Redundant Array of Inexpensive Drives</i>

It's Independent. Independent meaning physically independent from one another. You don't get any security by creating a virtual RAID1 array on two partitions of a single physical drive. I don't but the Inexpensive part because the first RAID controllers were SCSI controllers, hardly what one would describe as cheap.

 

[jim552]

I prefer to maintain the use of "inexpensive".

I think this is still valid, and I believe it is more valid now with the use of "standard consumer drives" in RAID configurations.

When this concept was first published in 1988 by Patterson and Katz, the "I" did indeed stand for "inexpensive".

Yes, the first RAID systems were likely SCSI. Even so when SCSI was first introduced as it's first incarnation as SASI it was indeed a "less expensive and cheaper standard to the proprietary systems" that were predominant amongst systems manufacturers. It was still considered a "less expensive" alternative when it officially became SCSI as well.

I believe it was EMC marketing people that asked for, and received, the blessing of Randy Katz to change the "I" to "independent". I think that occured sometime in the 90's. I am guessing after 1995.

I would guess that if some-one delved deep enough, they would discover that this change was prompted by EMC Marketing so that customers wouldn't come to expect an "inexpensive product" from EMC that was based in "inexpensive disks".

 

[arkus]

If you don't know what striping and mirroring are, why do you want to setup RAID? Just get the biggest drive you can afford and don't RAID it. RAID is just not necessary for typical desktop users, deal with it.

As always, I would refer you to the guide at storagereview.com

<A HREF="http://www.storagereview.com/guide2000/ref/hdd/perf/raid/index.html" target="_new">http://www.storagereview.com/guide2000/ref/hdd/perf/raid/index.html</A>



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[mozzartusm]

Necessary? Its been a long time since half of the crap we put in our systems was necessary. RAID isnt necessary but it is a great tool and yes, the desktop user has plenty of reasons to go with a RAID setup.

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[fishmahn]

What Jim said.

In the PC arena SCSI is expensive. But RAID was first developed for use on larger systems - minicomputers and mainframes. Installing 3 or 4 SCSI drives at $2-3k each was less expensive than paying 20k+ for a single drive with less capacity and no redundancy. Even if the drives were less reliable (they were), since it was set up in RAID5 (most common use back then), your data was more reliable because of the RAID.

I used to work on HP3000 minicomputers, and SCSI was 'cheap' by comparison to the normal HP drive.

Mike.

<font color=blue>Outside of a dog, a book is man's best friend. Inside the dog its too dark to read.
-- Groucho Marx</font color=blue>

 

[4Ryan6]

<A HREF="http://forumz.tomshardware.com/hardware/modules.php?name=Forums&file=viewtopic&p=61149#61149" target="_new">Educate Yourself</A>Thats what the <b>Stickys</b> are for!






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<P ID="edit"><FONT SIZE=-1><EM>Edited by 4ryan6 on 06/30/05 11:50 AM.</EM></FONT></P>

 

[arkus]

Necessary? Its been a long time since half of the crap we put in our systems was necessary. RAID isnt necessary but it is a great tool and yes, the desktop user has plenty of reasons to go with a RAID setup.

Fair point. But in reality, I don't see how typical users notice much of a benefit from RAID. And if it is someone who is not experienced with RAID it could simply cause a whole boat-load of problems for them.

<A HREF="http://forums.btvillarin.com/index.php?act=ST&f=41&t=2765&st=0#entry21597" target="_new">My Rigs</A>

 

[kkrouse]

I am no expert by any means but what kind of onboard controller do you have? Or are you talking about a pci ide controller add on card? Or are you talking software raid?

 

[pat]

Fair point. But in reality, I don't see how typical users notice much of a benefit from RAID. And if it is someone who is not experienced with RAID it could simply cause a whole boat-load of problems for them.

I can tell you that I'm a typical user and I benefit from raid since 2002 when I first use it. And it is not more difficult to set up, when you read the manual.

Problem is that peoples thinks they know everything so they overlook the manual. then, they try to install the nvidia RAID with the Promise controller ...

Then they come here and ask.. without first reading the FAQs of course...

When I did my first array, I was not experienced, but I read the manual, learnt that I have to move a jumper, then enable RAID in BIOS and then, setup the array. When done, I rebooted and install windows with the correct drivers by pressing F6..

All the mobo I had, since that one always had RAID on them, and I never had a single problem. The manual always have a section about RAID too. You wont go anywhere if you have the best driving map, but you didnt take the effort to learn how to drive a car... Just like RAID, if you dont have a clue about what and why, you will have problem. well just like anything.. RAM, video card, sound card....

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