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g725s

P410 controller and RAID 1 vs. RAID 1+0

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g725s

As I have a P410 controller in my N40L MicroServer I am able to make a RAID 10 array with the four 4tb drives that I have.  Doing web searches I am trying to understand why someone would choose RAID 1 or 10 (1+0) over the other.  I would like to hear some of your thoughts and opinions on this subject.

 

Would the type of drives used dictate a decision as to go with one of these two types of RAID over the other?  Specifically with basic 4tb desktop drives like the HGST Deskstar drives that I have?

 

Does anyone that participates here in the forums on a regular basis use RAID 10?

Edited by g725s

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schoondoggy

Here are some clippings from http://www.proprofs.com/mwiki/index.php/Understanding_RAID_levels

 

RAID 0 

RAID 0 was not defined in the 1987 Berkeley paper. In fact, it is not RAID because it does not provide any redundancy. RAID 0 is just an array or group of disk drives used as a single disk. The data is written in chunks or stripes to all the disk drives in the array. This improves disk input and output performance because several chunks of data can be written or read simultaneously. If a disk drive in the RAID 0 array fails, all data in the RAID 0 array is lost. RAID level 0 is also often called disk striping without parity. Figure shows an illustration of RAID 0.


RAID 1 
RAID 1 requires a minimum of two disk drives. All other RAID levels, except level 0, require at least three disk drives to implement. RAID 1 writes all data to two separate locations. To store 20 gigabytes (GB) of data using RAID 1, two 20-GB disk drives are required. This is a 50 percent loss of storage capacity.

There are two ways to implement RAID 1:

  • Disk mirroring
  • Disk duplexing


In disk mirroring, the two disk drives are connected to the same disk controller. The only problem with disk mirroring is that if the disk controller fails, there is no access to the mirrored data. Figure shows a diagram of disk mirroring. To eliminate this single point of failure, use disk duplexing rather than disk mirroring.


In disk duplexing, each disk drive in the mirrored set is connected to a different disk controller. This eliminates the single point of failure in pure disk mirroring. The only additional cost is the additional disk controller. Figure shows a diagram of disk duplexing.

RAID 5 
RAID 5 uses block-level parity, but it spreads the parity information among all the disk drives in the disk array. This eliminates the parity drive failure common in RAID 4 systems. The loss of storage capacity in RAID 5 systems is equivalent to the storage capacity of one of the disk drives. If there are three 10-GB disk drives in a RAID 5 array, the storage capacity of the array will be 20 GB, which is a loss of one-third, or 33 percent. In another example, if there are seven 10-GB disk drives in a RAID 5 array, the total storage capacity of the array will be 60 GB, which is a loss of one-sixth, or 16.67 percent. Figure shows a diagram of RAID 5.


RAID 0/1 
RAID 0/1 is also known as RAID 0+1, and it is sometimes called RAID 10. This combination of RAIDs provides the best of both worlds. It has the performance of RAID 0 and the redundancy of RAID 1. RAID 0/1 requires at least four disk drives to implement. In RAID 0/1, there are two RAID 0 stripe sets, which are used to provide high input/output performance, that are mirrored. This provides the fault tolerance. Figure shows a diagram of RAID 0/1.

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g725s

Thanks Schoondoggy,  I found a similar page that compares the various types of RAID and says that RAID 10 is best for mission critical applications: http://www.thegeekstuff.com/2010/08/raid-levels-tutorial/

 

I'm just trying to get an idea of why someone with four drives available would choose RAID 1 or RAID 10 over the other as they provide roughly the same amount of available disk space.  However, RAID 10 seems to have better redundancy.

 

With my four drives I get:

 

RAID 0 , 14.5tb

2 sets of RAID 1 , ? , I'll assume roughly 7.2tb

RAID 5 , 10.9tb

RAID 10 , 7.2tb

 

I have read a few comments here of people using RAID 1.  One comment was "I'll be switching to RAID 1 with the larger  4tb drives".  So what I'm wondering is, if you have the ability with a controller card in your server, why not use RAID 10 over RAID 1?

 

For me it seems with the price of 4tb hard drives currently as they are, and as far as redundancy goes, that RAID 10 could be a good choice.

 

Also on a side note, since you have a P410 how do you get notification if  you have a drive failure.  I just tested pulling a drive out of a RAID 10 array I set up as a test and the only way I could see that there was a drive missing from the array was to open the ACU and see the notice there. 

Edited by g725s

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schoondoggy

Some may choose RAID 1 to keep things simple. You don't need a RAID controller, you can enable it in the OS. There is no performance benefit with RAID 1. The RAID 5 vs 10 debate is compounded by the RAID controller that is used and its ability to rebuild a RAID 5 parity sets. RAID 10 is less impact to a RAID controller because you are just striping and mirroring. Raid 10 is fast, but you only get 50% usable capacity. RAID 5 sets, you only lose the capacity of one drive. The bigger the drive, the longer it will take to rebuild a RAID 5 set. I still use RAID 5 on 3TB drives and I may use it on 4TB. I will need to see how the rebuild numbers look. If you want performance and protection and don't want to worry about RAID 5 rebuilds go with RAID 10.

Lets not forget, RAID is not backup. I have backup copies of all of my data. If a RAID 5 set ever completely died on me I would be able to repair and reload.

 

Drive failure notification, great question that I have not worked on yet. There is a event notification software package for the P410, but it appears to just work with Server 2008. Maybe others can share what they are doing for drive failure notification with P410 or other RAID controllers.

I am not sure if your test validated the notification testing or not. The P410 would treat that as a missing drive not a failed drive and would treat it differently, I think. Hopefully others have data to share.

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g725s

Thanks Scoondoggy, that gives me a better understanding of RAID 1, 5, and 10.

 

One thing I wonder about for RAID 1 and 10.  You can just theoretically pull a drive out from a RAID 1 and install at another computer, right?  What about RAID 10?

 

 

But as far as drive failure notification what software do you have to monitor?  In the P410 QuickSpecs it talks about the HP Systems Insight Manager.  I'll download this and see:

http://h18013.www1.hp.com/products/servers/management/hpsim/index.html  (hope the links works and HP links seem to be dynamic).

 

Any idea if you buy the P410 in a new retail box what software package it comes with?  As it seems most are getting used cards off eBay that are out of the box and without an installation CD.

 

Since I'm not finding the answers about this software via search here I'll make another thread over in the Microserver forum concerning this software and WHS 2011

Edited by g725s

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ikon

OK, I'll admit, I don't know if this is still true but, at one time, RAID1 could only use 2 drives. That was the main impetus for RAID10 coming along -- people said, "what if we could stripe drives together into two RAID0 arrays and then mirror the arrays; we could get much bigger arrays that way?". Do today's RAID cards allow multi-drive mirrors, without calling it RAID10, because to me that's essentially what they are, RAID10?

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g725s

My P410 only allows two drives to be RAID 1.   I had to select all four of my data drive to bring up the RAID 1+0 option.

 

See post #3

Edited by g725s

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ikon

OK, so it is still true, at least for some controllers.

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g725s

Still wondering about being able to pull drives out of RAID 1 and RAID 10. Can you pull drives out of these arrays setup on a P410 or similar HP Controller card (Windows environment) and read the content on another PC? My understanding is you can with RAID 1. Can you also with RAID 10?

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ikon

RAID1, yes. RAID10, I doubt it. Here's my thinking (and like I posted earlier): RAID10 is typically made up of 2 RAID0 arrays that are mirrored. You can't normally pull a drive from a RAID0 array and read it standalone.

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