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Redudancy in Dell Perc3/QC controller and RAID10

Posted on 2003-03-05
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Hi,

 My last system(Dell PowerEdge 4400) died because it seems the Perc controller corrupted the main container of RAID5 config, backing up from tape was not 100% successful.  We are getting a new system with a storage array of  6 146GB disks( 3 as one stripped set and 3 more to mirror the first).

Now the controller is a Dell Perc3/QC with 2 internal and 2 external channels.  When Dell helped me trouble shoot this they concluded that the container was corrupted by the contoller because it was running old firmware. Can this setup prevent this from happening again?  If the controller corrupts the primary set, will it currupt the mirrored set?( I think so)  I'm also not sure how the 2 internal channels work. Would one channel connect to the primary set and the other channel connnect to the mirrored set? And the external channels allow for more mirrored sets(arrays)? Does each channel have a backplane for each array of drives?

Thanx,

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Question by:blaqb0x
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LVL 8

Accepted Solution

by:
heskyttberg earned 400 total points
ID: 8074894
Hi!

Well this is very dependant on what you buy from dell.
How the drives will map to containers is up to you or whoever configures them to decide.

If you get a new server, go into the RAID controllers BIOS and check how the containers are setup.

You can setup one container on one channel and the other on the other channel.

This however wouly require you to buy the 3x2 optional backplane.
Standard backplane is 1x6, at least in our contry.

If you run mirror on same controller just two diffrent channels and first get corrupted, I'd say chances are very big that mirror also get corrupted since the controller mirrors all data from on container to the other.

Keep good backups, and also backup the RAID config from the card.

As for the two external connectors, they are usually same channels as the two internal.

So 2 internal and 2 external maps to:
Channel 1   1 int and 1 ext connector
Channel 2   1 int and 1 ext connector

Unless the card manual sais it has four channels.
If it has 4 channels however, the two external will each be on their own 'backplane' on the card.

Regards
/Hans - Erik Skyttberg

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Assisted Solution

by:russ960
russ960 earned 400 total points
ID: 8076251
Hello blagb0x,

I'm not sure what controller you have on your PowerEdge 4400 but since you used the term "container" I'll assume it is the embedded PERC 3/Di controller.   This controller is suseptable to the problem you described.  Now with that said you could encounter any number of RAID corruption problems on any RAID controller, including stripe corruption.  This corruption will affect you reguardless of the raid type.  

One problem with the RAID setup you described is that it is impossible on a PERC 3/QC.  When you have 2 3-Drive RAID 5 sets and you configure them on the PERC you would yeild a RAID 50 in which the data is striped across the 2 RAID 5 sets.   The only way to accomplish what you described with a mirror is by setting up 2 hardware RAID 5/0 sets on your PERC and then mirroring them with your OS.  This would be highly ineffecient and but it would give you the desired RAID configuration.  

Now on the controller you can do these via 2 channels or 1 channel either one would work.  One issue would be the backplane if you were using the 2 channels.  Your backplane would have to be a 2 channel or splitable backplane.  Also, one correction to the information you had on the PERC 3/QC it has 2 internal channels (Channel 0 and 1) and 4 channels externally (Channels 0,1,2,3).  If you attach anything to the internal channels DO NOT attach anything to the corresponding external channel.  

I hope this information provides some degree of clarity on this.  If you are looking to set these up as RAID 10 for redundantcy and performance reasons you could set this up as 3 RAID 1 sets then span them on the contoller.  Thank you.  
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Expert Comment

by:heskyttberg
ID: 8078292
Hi!

I never suggested 2 3 drive raid 5.

I suggested One raid 5 over 5 HDs with one disk as hot spare.

I merly suggested putting 3 drives on one channel and the other 3 drives on the other channel, this is for increased performance, but this would require the 2x3 backplane just as I suggested in my first post.

If you want some better strategy you can do as we done in our larger servers.

2 HDs as mirror array for OS.
3 HDs as a RAID5 array.
1 Hot spare.

Regards
/Hans - Erik Skyttberg

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Expert Comment

by:russ960
ID: 8080470
Hans:

Sorry for the confusion I was referring to the orginal post.  I agree with you.  I was just trying to address the orginal question and clear up some possible misconceptions of the products capabilities and address what it can do.  Thank you and sorry for any confusion.

Russell Johnson
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Expert Comment

by:andyalder
ID: 8083486
The old system crashed from a firmware problem rather than a single disk failure so you are going to buy another one?




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Expert Comment

by:russ960
ID: 8084128
Hans:

Sorry for the confusion I was referring to the orginal post.  I agree with you.  I was just trying to address the orginal question and clear up some possible misconceptions of the products capabilities and address what it can do.  Thank you and sorry for any confusion.

Russell Johnson
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Expert Comment

by:russ960
ID: 8084139
Hans:

Sorry for the confusion I was referring to the orginal post.  I agree with you.  I was just trying to address the orginal question and clear up some possible misconceptions of the products capabilities and address what it can do.  Thank you and sorry for any confusion.

Russell Johnson
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Expert Comment

by:andyalder
ID: 8084175
You will find E-E much easier to use if you click the "reload this question" link on the top left under your profile rather than the browser's refresh button.
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Expert Comment

by:LucF
ID: 10122871
No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:

Split between heskyttberg and russ960

Please leave any comments here within the next seven days.

PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!

LucF
EE Cleanup Volunteer
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