Rebuilding a array raid 5

[ison67]

I have a
ProLiant ML350 G3
Smart Array 641 Controller
I need to rebuild it. Please send me a link to documentation on how to do this. I want to set it up for Raid 5. Let me know if you need additional info.

Regards,
DJ

[Taifur]

Hi Ison67,

For RAID5 you need minimum 3 harddisk.
Steps,
1. Plug in 3harddisk or morethan 3 harddisk into the harddisk bay.
2.power on the server
3.When Array controller display, press F8
for ORCU(Option Rom COnfiguration Utility)
4.After access ORCU there 3 option
Create Array
Delete Array
View Array.
5.Press create array, then select your required disk , and select RAID 5

6.After creating press F3 for saving the array configuration
7.Then reboot the server
8.Again, press F8 for accessing ORCU , and check the array by view array pressing

The above procedure is for creating a new RAID5.

If it helps, pls assign point.

Rgds,
Taifur

[donna johnson]

Why do I need a spare drive for my array?

Regards,
ison67

[donna johnson]

I deleted and rebuilt the array. Surely there is more to it than this... I created it with 4 72GB HD's with three for the array and I as the spare, Still not sure what that's for. And now Windows Server 2003 standard is installing.

I will blow it all away and do it again, once I get it setup. This time is just for learning. I've never worked with scsi's before, so I want to learn a bit and the best way I know to do that is hands on.

I will need this info when I upgrade our domain controllers to Windows Server 2008. Some of them have space issues.

Thanks for the info and any additional input. I will assign point to you after I get a reply. I wasn't sure if it would close the ticket.

Regards,
ison67

[Srinivas Suddapalli · Accepted solution]

Hi Donna,

The spare drive for an array is for redundancy. RAID 5 can withstand one drive failure of the three drives you created. But when we add a fourth drive as online spare, it kicks in if there is any failure of any drive in RAID 5.

Decision would be yours depending on criticality of data between storage space vs redundancy.

Regards,
Srinivas S

[donna johnson]

Ok, so what happens if I lose a drive and don;t have a spare? With the spare and raid 5 setup, if one goes down, I simply pull it out and replace it with a new one, it rebuits and that's it. Without the spare would the server just be down until I replaced the bad drive? I know if I lose two at the same time, I lose everything. I'm still not sure what the difference the spare makes unless it allows the server to stay online until you replace the bad drive and if that's the case, if you had the setup I have with the spare and lost two would it make a difference? Sorry for all the questions, I'm just trying to be clear.

Thanks,
Ison67

[Srinivas Suddapalli]

Hi Donna,

Without spare : If one drive has failed out of 3 drives in a RAID 5, as it has redundancy can withstand one drive failure the drive can be replaced with server running fine. Situation exists when the drive is failed and before replacing this drive, if another drive fails RAID 5 cannot withstand and hence volume or data is lost.

With spare: If one drive fails the spare drive kicks in and rebuilds automatically. Once this is completed you can replace the failed drive after which spare drive returns back to its spare condition. If any drive fails after that the spare drive would kick in and be available.

You are exactly right with two drive failures issue in RAID 5.

The concept of spare is expensive because of this unused disk always waiting for any drives which are part of RAID fails.

Regards,
Srinivas S

[donna johnson]

So the only real difference is without the spare the server would just be down until I replaced the bad drive and it rebuilts? I know how this works with the spare. I'm just having a hard time understanding what would be different witout it.

Regards,
Ison67

[Srinivas Suddapalli]

Hi,

You question: So the only real difference is without the spare the server would just be down until I replaced the bad drive and it rebuilts? -- No. Server would be running and the failed drive can be replaced but a second failed drive would cause data loss.

To avoid this failure we use spare drive which would be a idle drive waiting if any drive in RAID 5 fails to take over.

Advantage with spare is that the drive automatically kicks in and starts to rebuild.
Once rebuild completed if there is a second drive failed, then it can still withstand and you have the server running.

http://docs.hp.com/en/J6369-90050/ch01s02.html#d0e441
http://en.wikipedia.org/wiki/Redundant_array_of_independent_disks#Purpose_and_basics

Please do reply if you have further queries.

Regards,
Srinivas S

[donna johnson]

Thanks for the links. Another question, how does what drive the array controller set on effect this? I ask because when this server went down, it had a spare and we lost one drive and the drive with the controller on it went down and the server could not recover.

Thanks you have been so much help.
Regards,
Ison67