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Old 08-28-2004, 08:17 PM   #1
jonthelam
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Question Rocket Raid 100


I'm a bit confused to what's the difference between hardware disk RAID and software disk RAID. From what I understand, isn't hardware RAID a card that emulates a RAID array of multiple drives as 1 drive? If so then why am I seeing 2 drives, /dev/hde and /dev/hdg on my Rocket Raid 100 controller card? Can someone point me to the right HOW-TO? I'm trying to setup RAID 1 and found drivers for this RAID card and quite frankly, I don't know what to do with them after I compile them into a new kernel.
 
Old 08-29-2004, 08:45 PM   #2
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bump
 
Old 08-30-2004, 01:55 PM   #3
jonthelam
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Wow this is the 2nd post that I have received no response for. Am I doing something wrong? Are the questions unclear? Do you guys need more info?
 
Old 08-30-2004, 06:47 PM   #4
Crazy Joe Davol
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Do you mean "what is the difference between a software raid and a hardware raid?"

To put it simply, a hardware RAID needs absolutely no drivers, TSR's, utilities, IRQ's etc in order to communicate to your operating system.
A hardware RAID controller needs only one thing from your system in order to work...power.

There are basically 2 levels of software raid. One level of software RAID can be a RAID controller the that has its own cpu and instruction set for creating a RAID, but because it may require a driver, it is still a 'software RAID'. This describes your rocket raid.

The next level of software RAID is implemented solely by the operating system or third party software, with no raid controller physically present.

The idea of any RAID is to combine multiple physical disks to be seen as one logical volume.

To answer your question, you havn't initialized the RAID yet. Your rocket RAID card is in JBOD mode. That is why it is seeing each drive independently (/hde and /hdg).

First, what kind of array do you want? RAID 1 or RAID 0?

RAID 1 is disk mirroring..the contents of one disk will be mirrored to the other, so if one fails, you wont lose your data. The amount of storage space will be equivalent to that of the smallest drive in the RAID.

RAID 0 is striping, and is for performance increase. The storage space will be the combined capacity of the drives in the RAID. But, if one drive fails, you will lose the data on all disks.

To initialize the RAID, you need to go into the RAID controller's BIOS. I think with highpoint cards its CRTL-H. Press this key combo during bootup.

When your in there, you need to select the drives you want to use in the array, what RAID type you want, etc. And you can also enable boot for the card (you must have this enabled in your computer bios as well).

Check out the website here:
http://www.highpoint-tech.com/USA/rr100.htm
The manual is availble for download there and can explain things better than be.
 
Old 08-30-2004, 09:15 PM   #5
jonthelam
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Thanks Joe. I have already initialize the RAID array in the BIOS level. I have 2 200GB HD set to RAID 1 and bootable. Only problem is that the OS isn't recognizing them as 1. But as you stated, its probably a driver issue, right? So does this mean I have to partition the drives individually and then have mdadm emulate the /dev/md# drive? I've printed out all the pertaining HOWTOs on www.tldp.org and will be reading further. Again, thank you for your help.
 
Old 08-31-2004, 01:55 PM   #6
Crazy Joe Davol
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Hmmm. Its really strange because if the Rocket RAID is reporting the array initialization as COMPLETE,
then Linux should not see 2 drives there at all. The Rocket RAId should only be reporting 1 logical device to Linux, not 2.
If linux us seeing both drives, then you shouldn't be looking any further than the Rocket RAID card. This is not a driver issue.
Double check the status of the array through the rocket raid bios. Perhaps there is an isse with the card itself?
 
Old 08-31-2004, 02:03 PM   #7
jonthelam
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I actually got the kernel to load the ataraid support and now it works as /dev/ataraid/d0 device. I was able to repartition and reinstall my entire distro. So thanks for pointing me in the right direction.
 
Old 08-31-2004, 03:56 PM   #8
Electro
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Do not setup RAID through the controller. Use Linux software RAID.
 
Old 08-31-2004, 04:08 PM   #9
jonthelam
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Electro, can you elaborate why software RAID is preferred?
 
Old 08-31-2004, 05:01 PM   #10
Crazy Joe Davol
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Using software RAID is somewhat of an oxymoron.

The idea of using RAID1 is for redundancy. Why would you put your data protection in the hands of your os?

Using a hardware RAID puts takes the control completely away from your os, freeing resources, and protcting against a disk failure AND os corruption/failure.
 
Old 09-01-2004, 05:11 PM   #11
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Man people are very confused between software RAID and hardware RAID. Your controller is not hardware RAID. What a hardware RAID is the controller has its own on-board CPU handling all RAID requests and the IDE or SCSI chip handle hard drives I/O requests. The chip that Highpoint, Intel, Promise, Silicon, SIS, VIA uses are just simple IDE controllers and the RAID is then handle by your main CPU. Making just IDE controller chips is much easier and cheaper. They, the manufacture, can then add RAID support later through software. With hardware RAID controllers, the OS will not see multiple hard drives that is in the array. The OS will see only one which is the final outcome of the RAID array. Using software RAID controllers you will all drives that is used in the RAID array including the final RAID drive.

The acronym forr RAID is very funny because it means different from manufacture to manufacture and there is different levels. RAID 0 does not give redundacy and in manufacture's words it gives security. In RAID 1 setups redundacy comes in and two or more hard drives are an mirror image. The hard drives in RAID 1 can be used individually and work the same as a single hard drive would. Next is RAID 5, using RAID 0 and spreading parity information on three or more hard drives. Again in the manufacture's words RAID 5 adds security and now redundacy which was lost in RAID 0. Using a stable and reliable OS like Linux to handle software RAID through it is several hundred times better than using Windows. IMO, I do not care what any manufacture say, RAID does not add security.

I hope by now people understand what is the difference between hardware RAID and software RAID. Also how redundunt each RAID level is.

Security for RAID is an oxymoron because your data is never protected by theives whom can rip out the hard drive from your case and access a third or half of you want you know. RAID, on certain levels, only protects your data from hard drive crashes. It never protects you from OS crash, unproperly shutdowns or reboots, viruses, hackers, or theives.
 
  


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