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Re-Initialization of RAID Hard Drives

Posted on 2013-11-09
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New Raid ConfigurationHi,

 I have LSI RAID controller with three 3TB HDs. I set up RAID 1 using first two hard drives and third one as hot spare. I started "Slow Initialization"  and basically took several hours. I created two partitions in RAID BIOS Configuration Utility - first partition with 2TB and second partition with 1TB. I loaded OS(SBS2011) in the first partition.

But I changed my mind and I like to create a small partition with 300GB for just for OS and use the rest for the data. So I went to BIOS of RAID and erased previous raid configuration and created first 300GB partition.

With this, I  have two questions.
(1) Do I need to re-initialize the drives or volumes or can I just load SBS2011 onto this partition now?
(2) Is it necessary to create the rest of the partition in RAID BIOS Configuration Utility now for the remaining 2.7TB or can I do it in Windows Computer Management program?

Thanks.
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Question by:sglee
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Technodweeb earned 300 total points
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1. If you changed the RAID configuration, and you are starting with a fresh build, absolutely reinitialize the drives to flush out any oddities that might creep up on you later. Why wouldn't you, except for the time involved. Long run, it will be worth it for peace of mind.

2. No but it is suggested so that the Windows installer can see it and configure it during the installation process. Really this is an either / or option.
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by:andyalder
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I'd leave creating the second logical disk until Windows is installed just because that way you install Megaraid Storage Manager so you get a bit of experience using both.
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by:dlethe
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Fast initialization means creating parity only based on the contents of every physical block.  Slow initialization (on this controller) adds a step of writing zeros to every non-parity block, and writing 1s (or 0s as need be) to the parity blocks.

There is no need to do slow initialization ... ever, but it is best practice because it has potential to weed out a HDD that will l likely die of infant mortality.  

The filesystems do not care about blocks that are not associated with data.  As such there is no inherent need to do slow initialization.  

1) So answer is no.
2) The RAID BIOS partitioning is different than the O/S partitioning.  The BIOS partitioning creates 2 logical HDD "physical volumes" s that are unique target disks.   The O/S partitioning slices up a specific physical volume into partitions.   You always have to do the O/S partitioning.

The BIOS will never see partitions you create with your file system. It will see the logical or physical volumes that the controller presents.   The O/S will see both the physical volumes as well as partitions.

Note that unless you have a UEFI BIOS, then the largest Physical partition that the hardware can boot will be FFFFFFFE hex blocks, or approx 2.09TB.
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by:sglee
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Thank you for expert opinions and I appreciate it.

(1) Regarding Initialization, the consensus is that yes I need to re-initialize. As to fast or slow initialize ... LSI tech support asked me on the phone yesterday to do "slow initialize", so I just started doing slow initializing.

(2) As to whether to create additional partition in - RAID BIOS or - Windows Computer Management or - Megaraid Storage Manager, I am torn since opinions vary...
Practically speaking, it should not make any difference right? When I created 2nd partition in RAID BIOS last night, Windows Computer Management showed the partition and I simply formatted it. If I wait until SBS2011 is installed and run Computer Management, I would do it there.  Or I have not tried it yet, but as andyalder suggested, I could do it in Megaraid Storage Manager and format it in Computer Management.
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by:pgm554
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What are the makes and models of the drives?

IF you are using desktop drives,I highly discourage you from doing so.

If you are using desktop drives don't even bother with the LSI controller RAID,just use the built in M$ RAID one utility.

Using Seagate ES ,HGST Ultrastars or WD RE is better way to go,but it's your data.
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by:dlethe
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I am a LSI developer.  Fast re-initializing rebuilds parity only.  Technically that is all you need.  Reinitializing (slow) zeros everything.  Both make parity consistent.  If you want to zero all other blocks, feel free .... but this does not affect data integrity in the least.    

If this was my system, I would do the slow init as a burn-in,  but if the disks are known good and already have gone through this process recently, it won't buy you anything.

#2  Please understand that the filesystem partitioning is different.  It slices up whatever logical devices the BIOS or RAID controller presents.  The RAID partitioning slices up the HDDs and tells the BIOS how it will see things.  They are different beasts entirely.
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by:sglee
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@pgm554
I bought Enterprise class SATA. Yes I have purchased destkop class SATA, put them on the raid controller, and paid the price dearly. So it won't happen again.

@dlethe
If you prefer the idea of creating a new partition in Computer Management, is there a benefit in doing so from practical standpoint?
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by:dlethe
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First, you HAVE to do this if running Windows. But beyond that, yes, you can have one partition with NTFS chunk of 64KB, as example, which is optimal for SQL Server, and make the C drive use standard NTFS which is for general use.
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by:sglee
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@dlethe
OK. I am installing SBS2011 on 300GB partition right now and once IS install is complete, then I will run Computer Management to create 2nd partition for 2TB (so that I can do Windows Native Backup with 2TB limitation) for data and create the last partition with remaining space for something else.

Thanks all for your suggestions.
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by:dlethe
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As long as the RAID controller presents a 300GB logical volume and a 2000GB logical volume, OR you have  UEFI BIOS and it is enabled.

But if your controller is presenting a single volume > 2.09TB and you DONT have UEFI BIOS, then this will not boot and you are wasting your time.
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by:sglee
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@ dlethe
Since we are on the subject ... I have a question about UEFI and BIOS mode in BOOT Mode (in my DELL T110 Server).
Yesterday when I opened brand new LSI Controller and put it in the serve, I could not get into RAID BIOS screen even after pressing press <Ctrl>-<H> during boot process. I found out that boot mode was set to UEFI. While talking to LSI tech support, I changed to BIOS mode and then I was able to press <Ctrl>-<H>  to get into RAID BIOS screen.

That said, I thought you are supposed to set the boot mode to UEFI if you have a partition larger than 2TB??  Do you know why I had to change the boot mode to BIOS to get into LSI RAID BIOS to configure raid?
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by:sglee
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@dlethe
After loading SBS2011, I ran Computer Management and it does not show the rest of the RAID volume (about 2.7TB). Should I create the 2TB volume using Mega RAID management software first?
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by:sglee
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sorry I forgot the screenshot of Computer Management.Computer Management
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by:Technodweeb
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You will have to allow the MegaRaid software control the logical partitions. Windows will only know about the partition via the LSI drivers.
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by:sglee
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@Technodweeb
OK. I will do download Mega Raid Management program from LSI website and install it.
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by:Technodweeb
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The reason in more detail is that Windows only sees the controller. The controller is emulating a physical drive(s). Windows will only be able to use the logical emulation devices if drivers are installed and configured to report the device to windows.
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by:sglee
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In summary,
(1) In Raid BIOS at boot time, I created an raid array and created 300GB "virtual drive" to load OS.
(2) When I finished setting up SBS2011 and ran CompMgmt.msc,  I was expecting to see 2.4TB partition, but it was not there.
(3) I download MegaRaid Manager and created two more virtual drives - 1.99TB and 400GB.
(4) Ran CompMgmt.msc and I saw two partitions then.

Thank you for your help in this matter.
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