[nflug] RAID

Corey Reichle coreyreichle at verizon.net
Mon Feb 11 15:02:49 EST 2008


After pulling the drive, you will need to "fail" the drive with mdadm.  After replacing it, you "unfail" the drive, and it will be gin to rebuild it.

=====================
From: Eric #4011 <eric at bootz.us>
Date: 2008/02/11 Mon PM 01:53:10 CST
To: nflug at nflug.org
Subject: Re: [nflug] RAID

No, I don't and definitely want to learn, since it is not being used by 
any users yet this would be the perfect opportunity.  I would like to 
know how to rebuild it.


Corey Reichle wrote:
> If you don't mind rebuilding it, pull a drive :)
>
> =====================
> From: Eric #4011 <eric at bootz.us>
> Date: 2008/02/11 Mon PM 01:30:33 CST
> To: nflug at nflug.org
> Subject: Re: [nflug] RAID
>
> Ok, my new system is in working order.
>
> Now I want to test a hard drive failure, any thoughts on how I should 
> approach this?
>
>
>
>
> Eric #4011 wrote:
>   
>> Ok, decided
>>
>> /boot                  RAID1   3 active and 1 spare  -1GB
>> /SWAP               RAID1  3 active and 1 spare   -2GB
>> /                         RAID5  3 active and 1 spare   -MAX
>>
>> then made / RAID 5 and LVM volume group
>>
>>
>>
>>
>>
>> Eric #4011 wrote:
>>     
>>> I really like the RAID 0+1 idea but I'm not sure how to do it with 
>>> Linux software RAID, do I need to create two RAID 0's and then 
>>> combine them with a nested RAID 1 to achieve RAID 0+1.  I will 
>>> consider RAID 5 as suggested.
>>>
>>>
>>> Corey Reichle wrote:
>>>       
>>>> 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
>>>>>>     _______________________________________________
>>>>>>     nflug mailing list
>>>>>>     nflug at nflug.org <mailto:nflug at nflug.org>
>>>>>>     http://www.nflug.org/mailman/listinfo/nflug
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> -- 
>>>>>> -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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