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RAID 10 or RAID 01??

Posted on 2004-10-11
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Last Modified: 2010-05-18
Hello,

I have a question about the difference between RAID 10 and RAID 01, believe me, I did all the research I can, and read all the technical terms like stripped mirrors or mirrored stripes, but I can't really find exactly why a scenario would prefer one of the two.  I think what I really need is an explanation in english.

I have a datawarehouse project next month and the database size gets to over 500GB.  I need exceptional IO performance hence I choose this RAID setup over the RAID 1/0/5.  

Also, can someone tell me how is the IO overhead comparison between 5 and 10?

Thanks experts,
Phillip
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Question by:phillipy
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by:Cyber-Dude
Cyber-Dude earned 250 total points
ID: 12274784
As for the first question:
RAID 10 usually involves four disks and two technologies; Striping and mirroring.
RAID 01 is only mirroring.

As for the second question:
RAID 5 is a great architecture for both reliability and performance.
RAID 10 may provide you with performance and reliability as well.

As for the third question:
I would use a RAID 10 (and that is my opinion) due to the fact it may take some time to reconstruct a faild drive in the event of a need for drive replacement.

Links:
RAID Levels and how they work?
http://www.acnc.com/04_01_00.html

More info?

Just say so.

Cyber
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by:Cyber-Dude
ID: 12274821
PS

Did you mean RAID 0+1?

Anyway; RAID 10 is my favorite.

Cyber
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by:phillipy
ID: 12274844
hello Cyber,
thanks for ur reply
is there a difference in RAID 10 and 1+0  or RAID 01 and 0+1?
please describe.
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by:Cyber-Dude
ID: 12274904
Phillipy,

I provided you a great link where you can see all the available RAID technologies available on the market; how they work (the draw the whole thing so it could be easy to view exactly how and where the data is running) and what advantages and disadvantages each technology has. Also, it descibes the reccomendation usage for each technology. Great link, great article.

Cyber
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Author Comment

by:phillipy
ID: 12274931
yes, u have, and i have seen the link before this posting
but please review the link below:
http://www.experts-exchange.com/Storage/Q_20683243.html?query=raid+10+and+raid+01&clearTAFilter=true

on 07/23/2003 09:39PM PDT there are people talking about the diagram in AC&NC providing wrong diagrams, that is why i am wondering who is right and who is wrong.
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by:phillipy
ID: 12274937
also in that link, it does not have diagrams on 01, only 0+1 so i can not make a comparison on 01 VS 0+1 and 10 VS 1+0
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by:Cyber-Dude
ID: 12275017
There is no plain 01 RAID but 0+1 (which is referred to as 01, 0/1 or 1+0 in some cases). In the link you can see the BIG difference between the two RAID 10 and RAID 0+1 in data streamming. You can compare the two by seeing the mapping of the two RAID architecture and read the advantages and disadvantages. Also, you have requirements to establish the RAID properly.

Hope that answers your question

Cyber
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andyalder earned 250 total points
ID: 12275056
RAID 10 is the same as RAID 0+1, you create mirrors and then stripe them.

RAID 1+0 or RAID 01 rarely exist, they would involve creating two stripe sets and mirroring them, same performance under normal poeration but if one drive fails then the whole stripe is down so you get a big performance hit.

RAID 10 is fast reconstructing a failed drive as it simply has to copy the mirror, RAID 5 is slow reconstructing a failed drive since it has to read all the other disks instead of just read the mirror, it also goes very slow with a failed disk.

I would agree that acnc has got it wrong, what they have called RAID 0+1 is what everyone else calls RAID 1+0, most controllers don't even support it since there is no sense in doing it that way.
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by:Cyber-Dude
ID: 12275120
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by:andyalder
ID: 12275298
The problem is one of terminology, some manufacturers will call it RAID 0+1 and others will call the same thing 1+0, as long as the mirrors are created before they are striped then the best performance will be achieved with a drive failure and while rebuilding.

There's even confusion within the same manufacturer, Compaq call it RAID 0+1 whereas HP call it RAID 1+0 but what's in a word? As long as the mirrors are created first is all that matters.
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by:Cyber-Dude
ID: 12275380
You are right on that one but mirrors are created in a different manner thus it is logical to think that 10 is actually 1+0 and 01 is actually 0+1 which are totally different consepts. Correct me if Im wrong...

Cyber
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by:andyalder
ID: 12275403
See http://www.meteck.org/RAIDusage.pdf for example, the difference betweeen Mylex and the Berkley standard of RAID 0+1. They are both called the same but differ in whether to stripe or mirror first. I use the DEC HSG80 terminology since it supports both.

So we really need to know what controller phillipy is using to see what that particular manufacturer refers to as RAID 10 or 0+1 or 01 or 1+0.
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by:Cyber-Dude
ID: 12275651
Hehehe...

It is amazing... But I think I have it;
The report you sent me did actually issued the names and how Mylex, for instense, calls RAID 0+1 as Fist striped and than Mirrored... well the authour is just mistakin... it is simply not true because Mylex claims otherwise:
http://lsionline2.lsil.com/esupport/esupportlsi/consumer/esupport.asp?id=cff7d451-f111-4eb1-9b19-de71291b4b9f&resource=&number=3&isExternal=0&nShowFacts=&nShowCause=&nShowChange=&nShowAddInfo=&activepage=statement.asp&bForceMatch=False&strCurrentSymptom=raid+0%2B1&searchtype=normal&searchclass=QuickSearch&bnewsession=false&selecttype=match
>RAID 10 is created by spanning two RAID 1 sets.
And that is the true aspect... and which is equal to:
http://www.acnc.com/04_01_10.html

:)

Now I see where it is comming from...

But thanks for enlighting the market situation... things may be comfusing and ppl may be comfused...

hehehe

Cyber
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by:andyalder
ID: 12275741
That was a particular Mylex chip, it would not apply to the megaraid controller.

The author wasn't mistaken when they said "RAID level 0+1 and/or level 10 can trigger a lovely and lively endless discussion
among RAID experts about the exact naming, 0+1 or 10, and the exact implementation."

Generally we talk about 0+1 being synonymous to 10 and 1+0 not existing at all or being synonymous to 01. acnc.com are out of step in that they call 0+1 what most others call 1+0.
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by:Cyber-Dude
ID: 12275843
I disagree but...

I think the more important issue here is maybe that the author should just ask the manufacturer (or the dealer for that matter) the meanning of the RAID 1+0 or 10 or 01 or 0+1 before puchasing any adapter while taking in-mind our reccomendations as mentioned above...

Cyber
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Author Comment

by:phillipy
ID: 12276472
wow you guys are too advanced for me!  but thanks for all your efforts, frankly I do not know what manufactuer it is because it is of my customer's hardware.
however, i dont think i will find out because all i wanted to know was simply if my data warehouse should use the RAID 10 or 01 over RAID 5, so I will except all of your answers and ask my customers to convert to RAID 10 or 0+1
thanks.
i will split the points.
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by:Cyber-Dude
ID: 12276540
I think you got your answer already:
See, RAID 5 is a great technology you can use but most likely RAID 10 is your best choice... there is no contreversion here.

Cyber
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by:andyalder
ID: 12277722
RAID 10 will be faster than RAID 5 for the same amount of data, but it will require more disks,
say you have 5 disks in RAID 5 then you would need (5-1) * 2 = 8 disks in RAID 5
Most RAID controllers can convert from RAID 5 to RAID 10 'on the fly' although obviously while
migrating the array level it will slow down a bit.
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by:josephhand
ID: 12463027
The one fundamental thing that I did not see (maybe I am skimming instead of reading ;-) ) is that one can sustain multiple failures and one can not. If you have a stripe and then mirror it to another stripe, you get redundancy and performance. What you don’t get is failure protection of more than one disk. This is usually referred to as 0+1, but can be named anything by a particular vendor or another, mileage may vary… The other way to lay out disk is to create mirrors of all you LUNs first (however many you will include in the set), then stripe them. This is usually called 1+0 or RAID 10. Again, names could be change from vendor to vendor, so look at the technology, not the name. The benefit this layout offers is you can now sustain multiple failures, so long as they are not on the same mirrored set. See diagram below.

0|2|4|6|8|10
1|3|5|7|9|11

You could lose all even or all odd and still maintain performance and access. You could also lose, for example, disk1, disk6, and disk9 and still not lose access.

As far as layout and number of LUNs you use for performance, the vendor should be able to help you calculate these based on your requirements and nothing else. Your application and the number of I/Os it manages to generate are all that matters here. There is no way that I could tell you, based on what I know from this thread, how many you need. Only performance monitoring can do that.

jh
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