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Old 09-14-2006, 04:05 PM   #1
darren.newdick@gmail
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Hardware Raid on FC3


I have been working with Linux for some time now and still learning every day you could say I am hooked Linux nut this question maybe a silly one but I need to ask maybe someone can call me a numb nut if they want if the question sounds silly but this is getting to me but I can not find an answer anywhere? Now for the question.

I have two hardware raid setups using sil cards and sata drives two drives are configured on the mother board raid as mirror all ok installed new raid card with drives and setup as raid 5 not a problem but I am confused why Linux see all 5 drives what I mean is if you setup the same on windows machine windows sees the raid set not individual drives.

When I login to Linux with webmin and go to the Partitions on Local Disks section webmin sees all the drives a single drives and not just two drives.
So in if I was not around this would allow somebody to create a new partion on any fives drives which would not be good.
Example on Webmin
-------------------------------------------
Mirrored set as /dev/sdd3 mounted as /
This drive is part of the hardware mirror set /dev/sde1
No partion at all blank

Why does Linux & webmin see both these drives as they are part of a mirrored set?
-----------------Raid 5 Set Below---------
I have tree 115gb drives on hardware raid 5 set which should give me 223GB approx to use which is mounted on Linux as /home /dev/sda1 but fc3 and webmin sees this drive as single 115GB. And sees the other two drives in raid 5 set as the same.
----------------------------------------------------
Can some shed some light why this happens or am I do some thing wrong I checked raid setup at boot time with raid utility all raid is configured properly no errors why does fc3 see all 5 drives and not identify the raid sets as one drive mirrored which would one x 80GB drive and the raid 5 set as one X 223GB as second installed drive????????

Hope you understand What I have wrote I need to find out why Linux does this or is there way of configuring Linux to hide drives which are part of hardware raid set?

Thank You
Webie

Last edited by darren.newdick@gmail; 09-14-2006 at 04:12 PM.
 
Old 09-14-2006, 04:30 PM   #2
Electro
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A lot people do not understand the difference of a RAID controller. There are two kinds of a RAID controller. One is a hardware RAID and the other is a software RAID. A hardware RAID contains an IDE, SATA, or SCSI controller chip, a processor, memory, and additional chips like an XOR chip to handle the input and output tasks and to off load the main processor. A software RAID controller leaves out a processor, memory, but it may have an XOR chip to speed up RAID-5 tasks. A software RAID controller uses the main processor and main memory to do all the input and output tasks of RAID. A RAID level 5 needs a lot of processing to handle the task, so I suggest multi-processor system. Linux sees all drives on the RAID array on software RAID controllers because it does not use the BIOS for many task.

The controller you are using is a software RAID controller. In order to use your RAID array, you need to use device mapper utility. Not all distribution comes with this and Fedora 3 is old. Also Silicon Image controllers are horrible because it corrupts data and turns DMA on and off. If you want a real hardware RAID controller and bring proformance back to your computer, I suggest 3ware controllers. As of kernel version 2.6.14, all 3ware controllers are supported.
 
Old 09-15-2006, 04:25 PM   #3
darren.newdick@gmail
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Many Thanks

Quote:
Originally Posted by Electro
A lot people do not understand the difference of a RAID controller. There are two kinds of a RAID controller. One is a hardware RAID and the other is a software RAID. A hardware RAID contains an IDE, SATA, or SCSI controller chip, a processor, memory, and additional chips like an XOR chip to handle the input and output tasks and to off load the main processor. A software RAID controller leaves out a processor, memory, but it may have an XOR chip to speed up RAID-5 tasks. A software RAID controller uses the main processor and main memory to do all the input and output tasks of RAID. A RAID level 5 needs a lot of processing to handle the task, so I suggest multi-processor system. Linux sees all drives on the RAID array on software RAID controllers because it does not use the BIOS for many task.

The controller you are using is a software RAID controller. In order to use your RAID array, you need to use device mapper utility. Not all distribution comes with this and Fedora 3 is old. Also Silicon Image controllers are horrible because it corrupts data and turns DMA on and off. If you want a real hardware RAID controller and bring proformance back to your computer, I suggest 3ware controllers. As of kernel version 2.6.14, all 3ware controllers are supported.
Many thanks for explaining where i was going wrong you a right about the sil raid card since this post lost the server today but have managed to get wesites back from drive and now going to upgrade to 3ware controllers and start gain hopefully for the last time.once agian thank you for your knowlage

Darren
 
  


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