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RAID Management query

Posted on 2011-03-16
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Last Modified: 2016-12-08
I have a server with a raid controller and 7 disks.

Each disk is 500 GB in size.

I want RAID 1 with 2 disks for OS. RAID 5 with 5 disks for data.

Problem is RAID 1 on 500 GB for solely OS is a waste. Can I somehow allocate 450 GB of the OS RAID 1 to the RAID 5?

In the DELL setup utlility it seems I have to use the entire 2 disks. Can I somehow manage this after the OS is installed?

I would like to see OS RAID 1 50 GB, DATA RAID 5 2 TB

Regards
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Question by:Network_Padawan
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Expert Comment

by:pcchiu
ID: 35152899
You can't do that as the hard drive physically in 500G.    

You can get 2x120GB hard drive for the OS and then save the 500GB for the RAID10 which may serve your purpose?

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Assisted Solution

by:Alan Hardisty
Alan Hardisty earned 25 total points
ID: 35152903
With 500gb drives using 5 for RAID 5, you will have 2TB of data anyway, but the short answer is that you can't allocate the 450gb of space on the RAID 1 volume to the RAID 5 volume.

I would stick to a 500gb C: drive and enjoy the space!
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by:pcchiu
ID: 35152904
I also suggest using RAID 10 instead of RAID 5 if possible.
http://www.cyberciti.biz/tips/raid5-vs-raid-10-safety-performance.html

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by:PowerEdgeTech
PowerEdgeTech earned 70 total points
ID: 35152943
I too would recommend sticking with two drives for the OS - or getting two high-speed, smaller drives for the OS.

OR...

Your controller will also support multiple RAID 5's across the same set of disks, so you could create a RAID 5 of 50GB across all 7 disks, then use the remaining amount in another RAID 5.  This is called slicing.  This cannot be done in the Dell installation utility.  It must be set up in the CTRL-R configuration utility during POST, then skip that option during the installation utility (or skip the use of the utility altogether).  You would end up with a data "disk" in Windows that is larger than 2TB, so you would have to convert it to GPT before partitioning it.
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Author Comment

by:Network_Padawan
ID: 35152952
Hi PowerEdge, I wasnt aware you could do slicing...will give that a try
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by:Network_Padawan
ID: 35152990
pcchiu, why would i go for RAID 10? I stand to lose 500 GB with that setup
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by:pcchiu
pcchiu earned 50 total points
ID: 35153065
I don't think you want to do slicing as if anything went wrong you may not able to recover any data, as RAID1 is the simplest raid and you can recover data and repair it easily.  With slicing in case anything went wrong it's make it much harder for recovery.

RAID 10 you gain on performance...  So if performance is more of the concern you may want to go for it, if the storage size is more important you can stick with RAID5..

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by:PowerEdgeTech
ID: 35153079
If you are using a Dell controller that will do RAID 5, it will also support slicing.

Which system/RAID controller are you using?

RAID 10 vs RAID 5 generally has better write performance (common for databases), and gives you "up to" two-drive fault tolerance (you can lose up to 2 drives and still have access to the data).  It does come at a disk/space cost though.
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by:PowerEdgeTech
ID: 35153127
Which is why I still recommend using two drives dedicated to the OS, but the controller can do it, if he is so-inclined to go that route.
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Author Comment

by:Network_Padawan
ID: 35153157
Hi powers,

Its a perc 7 card I believe
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Accepted Solution

by:
dlethe earned 105 total points
ID: 35153726
You really should just leave it alone BUT ...
Use the RAID1 for scratch table space; swap files; transaction logs; any write-intensive items.  Then not only do you accomplish "freeing up the space for data", but you also take advantage of the inherent write speed advantage of RAID1 over RAID5.

RAID10 is NOT going to be faster across the board, because on your O/S disk you're going to be doing a lot of 4KB I/Os.  If you so much as touch a file, and your stripe size in the RAID is 64KB, then you'll be forced to write 128KB worth of data every time.   RAID10 is better for a SQL database but not the boot drive, at least from the I/Os per second perspective.

Personally, I would leave things as they are.
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Author Closing Comment

by:Network_Padawan
ID: 35177105
Thanks guys. Will just leave it as is.
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