[nflug] RAID
Eric #4011
eric at bootz.us
Mon Feb 11 09:14:39 EST 2008
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
>>> _______________________________________________
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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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