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RAID 1 & RAID 5 / PowerEdge 2850 Server Question

Posted on 2004-11-04
Medium Priority
Last Modified: 2012-05-05

My company just bought a new Dell PowerEdge 2850 Server with the following setup:

RAID 1 - (2)18 GIG SCSI Drives
RAID 5 - (3)72 GIG SCSI Drives

With in Dell's Open Server Management under "Storage" it verifies the above referenced setup. When I go into My Computer I see the following.

C: 12 GIG
D: 136 GIG
E: 4 GIG

Is this correct? I am new to RAID, so pardon my ignorance.


Chris B
Question by:cbarone2004
LVL 86

Expert Comment

ID: 12497318
Seems about right.
RAID 1 is plain mirroring, so your two drive setup will effectively have the size of a single drive. The E: drive is probably a partition on your RAID 1.
With the RAID 5 setup, you'll have a net capacity of two (3-1) drives, one being "sacrificed" for fault tolerance.
Given that hard drive manufacturers usually define 1 GB as 1000MB, and 1MB being 1000KB, whereas Explorer uses multiples of 1024, you can calculate this back:
72GB*2=144GB = 144000000KB [HDM].
140000000KB/1024 = 140625MB [Exp]
140625/1024 = 137GB [Exp]
LVL 97

Expert Comment

by:Lee W, MVP
ID: 12497319
Hardware RAID takes all the drives and configures them in the RAID, then reports to the OS 1 (or in this case 2) physical drives that are equal to the size of the allowable space for that RAID.

In this case, the RAID 1 using Two 18 GB drives will report ONE 18 GB Physical Disk
The RAID 5 should report 3x72-72 (n-1x72GB - where n = the number of drives you have) or 144 GB.  Since the drive sizes for marketing are measured in 1 billion bytes (as opposed to 1024Kx1024Kx1924K = 1 REAL GB of data), the actual sizes will be a little smaller.

In short, yes, this looks fine.
LVL 97

Expert Comment

by:Lee W, MVP
ID: 12497341
Have a look at http://www.integratedsolutions.org/raid_ov.htm and http://linux.cudeso.be/raid.php for some descriptions of RAID.
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Accepted Solution

sunhak earned 750 total points
ID: 12497713
that is correct.
dell usually partitions the RAID 1 drives into 3..
one for management softwares in FAT format, (no drive letter assigned)
one for OS (c:) and another (e:)

d: is the RAID 5 drives.. so ~136GB

Expert Comment

ID: 12500488
That's correct if that's the way you want it configured. Don't let them put your OS on a stinking 4GB partition. Disk space is too dang inexpensive to have to rebuild your machine later because your numbskull dba has used the system partition for installing every piece of shareware known to mankind until you can't even boot the dang thing anymore. And no... I am NOT bitter!

Expert Comment

ID: 12501623
I saw the same thing - Dell for some reason doesn't like to configure your boot partition larger than 12Gb (if someone knows the reason please feel free to enlighten). Every Dell server I have ever received I have used the Dell Server Assistant CD and overwrote their configuration - having that 4Gb off by itself is basically useless. Combine it with the 12Gb on the system partition and save yourself headaches down the road. The RAID 5 array can probably be left alone however.


Just occured to me I'm assuming your using windows 2003 since its a new server, and win2k3 will support the larger boot partitions. There was a time when splitting the system partition off was a limitation of windows OS (2Gb, then 4Gb, now unlimited) and it seems some engineers are tied mentally to that.

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