[nflug] RAID

Corey Reichle coreyreichle at verizon.net
Mon Feb 11 08:42:07 EST 2008 

You need to consider this:  RAID0 is the best performance wise, but at the risk of a single drive going will bring down the array.

RAID1 will get you some fault tolerance, but it takes a hit since two physical writes for every logical write.  The only way to circumvent much of the performance loss is separate controllers.

I would suggest RAID5.  Best performance gain for fault tolerance, as well as increased performance over a RAID0 with the right controllers.

====================
From: Eric #4011 <eric at bootz.us>
Date: 2008/02/11 Mon AM 07:01:46 CST
To: nflug at nflug.org
Subject: Re: [nflug] RAID

Great, I'll use Raid Software then.

Space isn't a problem each drive is 160GB and it's just a small email 
server of about 100 people, so raid 0 or 1 would be best for performance?
these are also hot swap drives does a certain raid matter in this instance?

Thank you,
Eric

Mark Musone wrote:
> I'd probably use software raid over most onboard SATA raid controllers..
>
> You may also want to consider raid-5, since you'll get more usable storage
> space than raid0-1
>
> Mark
>
>
> -----Original Message-----
> From: nflug-bounces at nflug.org [mailto:nflug-bounces at nflug.org] On Behalf Of
> Eric #4011
> Sent: Friday, February 08, 2008 3:36 PM
> To: nflug at nflug.org
> Subject: Re: [nflug] RAID
>
> Yes it does help, and I want to be sure I do this the right way.  The 
> board is a TYAN Tomcat K8E using a Nvidia RAID controller for SATA 
> drives... I have heard that the onboard RAID controllers are not that 
> great, however which is better poison the Linux RAID software or the 
> onboard RAID controller?
>
> Rob Dege wrote:
>   
>> It's been a while since I've spoken in RAID, but I think your 
>> terminology is off.  RAID-0 by default requires at least two hard 
>> drives in order to configure.  The same goes for RAID 1.
>>
>> So, in this instance, you will use two drives to create a RAID-0 
>> array.  This array now appears as a single drive.  You then create 
>> another RAID-0 array using the other two disks.  This array now 
>> appears as a single drive.  So now, you have two RAID0 arrays 
>> independent of each other.  Finally, you create a RAID-1 mirroring 
>> array, using the two RAID-0 disks that you just created.
>>
>> Thus, you now have a single drive, with the capacity of two drives.  
>> If this is all handled within the RAID controller, linux will only 
>> acknowledge the existence of this RAID-0+1 drive as a single disk.  So 
>> you won't be able to use the linux software RAID to create another 
>> layer of mirroring.
>>
>> Of course, this is assuming that your RAID controller is doing all of 
>> the array structure and work.  Most of the onboard RAID controllers in 
>> today's motherboards, and built shoddy.  Their contain the cheap 
>> hardware, but you need to install software to configure/access the 
>> onboard controller.
>>
>> Plus, it's been a while, but I do recall some warning about not 
>> putting either the root directory or the /boot directory on a raid.  
>> It has something to do about the module needed by the kernel to 
>> identify the raid drive being stored on the raid drive or something 
>> like that.
>>
>> oh well, hope this helps somewhat.
>>
>> -Rob
>>
>>
>> On Feb 8, 2008 12:49 PM, Eric #4011 <eric at bootz.us 
>> <mailto:eric at bootz.us>> wrote:
>>
>>     Hi, I was wondering if the following RAID configuration is possible?
>>
>>
>>     I have 4 SATA drives for RAID and am using MediaShield utility to
>>     configure a RAID 0+1
>>
>>     
> ****************************************************************************
> *******************
>   
>>     MediaShield States RAID 0+1 is:
>>             RAID 0 drives can be mirrored using RAID 1 techniques,
>>     resulting in a RAID 0+1 solution
>>             for improved performance plus resiliency
>>             The controller combines the performance of data striping (RAID
>>     0) and the fault tolerance
>>             of disk mirroring (RAID 1). Data is striped across multiple
>>     drives and duplicated on
>>             another set of drives.
>>
>>     
> ****************************************************************************
> *******************
>   
>>     After this I have two drives and I am ready to install
>>     linux(debian etch)
>>
>>     My thoughts are if I also use RAID 1 software(linux) with the existing
>>     two drives I will have one hard drive writing to three hard drives?
>>
>>     I'm wondering if this is possible?
>>
>>     Thank you in advance for your explanations
>>
>>     Thank you,
>>     Eric
>>     _______________________________________________
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>>
>>
>>
>> -- 
>> -Rob
>>
>> Ben Franklin Quote: "They that can give up essential liberty to obtain 
>> a little temporary safety deserve neither liberty nor safety."
>> ------------------------------------------------------------------------
>>
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>
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