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3 Disk RAID need redundancy.

Tags:
  • NAS / RAID
  • Performance
  • Storage
Last response: in Storage
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November 22, 2007 10:03:13 PM

I know this question has been asked but everyone seems concerned about performance and don't care about losing their data.

My current setup is:
- Asus a8n-SLI Premium Motherboard
- nForce4 SLI AMD Chipset
- 2x WD2500KS 250GB HD's in RAID 1

I have another WD2500KS 250GB HD that I am considering adding to the Array in hopes to maximize performance while keeping redundancy. What RAID setup would be best given what I have said that HAS REDUNDANCY?

I have read that using the onboard controller can effect performance and that is why I created this thread, not sure if having a 3rd disk will help performance.

(RAID5?)

More about : disk raid redundancy

November 22, 2007 11:40:56 PM

In addition I have a 2nd question.

Should the PageFile stay on the C drive/RAID1. Would it benefit from the better read performance of the RAID?

Should the pagefile be placed on 1 single 3rd seperate disk on a small partition for itself while everything else is on the Raid1?
November 23, 2007 5:21:44 AM

Before you configure your WD2500KS disk drives to run under RAID controls, please note that the letters KS have a specific meaning.

I learned the hard way -- after buying two 500GB Western Digital Caviar SE16, WD5000KS RTL drives and trying to make them run reliably under RAID 0 controls – that Western Digital surreptitiously classifies their products as “Desktop Edition Hard Drives” or “RAID Edition Hard Drives.”

They claim that each type of hard drive is designed to work specifically in either a desktop computer environment or on RAID controller, but not both. And as you probably have already experienced, there is nothing at all mentioned about this fact on the packing material, user guide, or other printed material.

I spent countless hours talking to the WD customer support computer drones in India only to be told that my newly acquired drives are classified as desktop edition drives (as identified by the letters KS) and, hence, are not recommend for use in a RAID configuration. They also explained that they have a series of RE (RAID Edition) drives that are made to be used in RAID arrays and that these RE drives have something called TLER (Time Limited Error Recovery) which prevent the drives from going into a recovery cycle.

Please see the link below for more information.

Title: What is the difference between Desktop edition and RAID (Enterprise) edition hard drives?

URL: http://wdc.custhelp.com/cgi-bin/wdc.cfg/php/enduser/std...

To make the long story short, I finally traded my Western Digital Caviars for a pair of Maxtor 500 GB SATA II/300 internal hard drives.
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November 23, 2007 5:53:21 AM

If you are looking for the best combination of speed, size and data security, then your are on the mark by choosing RAID 5. In this case you need a minimum of three hard disk drives (I personally prefer using four identical drives).

RAID 5 is a hybrid combination of data safekeeping as well as speed. It doesn’t rely on mirroring (e.g., RAID1 or RAID 1+0) to preserve your data and information. It instead uses an alternative method of data redundancy found in RAID setups, namely “Parity.”

As a general rule, the mathematics of parity dictates that if you have at least three drives in an array, the RAID control will split each piece of data into three stripes. Each stripe will go to a single hard disk drive as it would in a RAID 0 configuration. The controller then creates a parity stripe based on the three stripes of data. A parity stripe is a logical calculation that allows the controller to re-create any individual stripe that becomes corrupt (or in the case of a drive failure, nonexistent). So, if you are faced with such a failure (it’s actually not a question of IF, but WHEN), then similarly to mirroring, the lost data is made available to the host computer instantaneously.

Yet, the loss of a single drive puts the entire array at risk. You should address this failure mode immediately by replacing the defective drive. If Murphy’s Law should strike and an additional drive fails, then all data on the array will be lost.
November 23, 2007 1:39:30 PM

Thanks for the informative reply. I've been running Raid 1 with these WD KS drives over 2 years now and they have been great. Can you explain to me if I missed something?

I guess I should rephrase my question as I'm 90% sure that Raid 5 is the setup I am looking for.

What will give me redundancy like Raid 1 but BETTER performance than RAID 1 since I have a 3rd identical disk to utilize? If the answer is keep it the way it is because the overhead for the onboard controller to manage the 3rd disk will negate the benefits then I'd like to know that as well.
November 24, 2007 4:19:12 AM

(1) Running RAID 1 with your WD KS drives over 2 years now certainly makes you a lucky camper. Nonetheless, it doesn’t guarantee flawless operation now or in the future. And, please, revisit the WD Web page and judge for yourself.

(2) I have given you my honest opinion about RAID 5 via the previous post.

(3) Should you keep your RAID 1 as a backup solution?

If you believe: “When one drive contents are always replicated (mirrored) on another drive, the RAID 1 configuration is the perfect backup solution,” then you are misguided.

Using a mirrored RAID as your de facto backup solution may work well during certain disastrous scenarios, such as one of your spindles spontaneously detonating. Yet, RAID 1 doesn’t prevent any of the more malicious (or often user created) data loss problems. If you have a virus raising its ugly head on one drive, for instance, it’s certainly been mirrored on the other drive. Or if you inadvertently perma-delete a file, or your machine cannot endure a power glitch, it’s gone forever on both drives. Comprenez-vous?

Moral of the story: If Murphy strikes on one drive, Murphy will, premeditative by design (RAID 1), strike on the other. And there is no going back in time!

I would grab some hard disk drive cloning and image backup software, such as ‘Acronis True Image’ for the safekeeping of my files on a dedicated (internal or external) drive and let RAID 1 (if I would feel obsessed to do so) take care of the act of good-type situations.
November 26, 2007 7:49:45 PM

I honestly don't see any point in moving from RAID 1 to RAID 5, unless capacity and performance are the key concerns. All in all, they both allow for one drive to fail. In doing data recovery for a living, we don't offer RAID data recovery services if there was more stability in have 5 drives then having 2.

In short, the RAID is a good method for redundancy, but should be followed up with a good backup routine that is regularly done and tested.
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