Re: RAID 1 versus RAID 5

From: Kevin Weilbacher [SBS-MVP] (kweilbacMVP_at_gte.net)
Date: 12/02/04 

Date: Thu, 2 Dec 2004 06:11:42 -0500

Reply to Fred -
your points are well taken and should be considered. I was simply addressing
the fact that posts and articles that say that you CANNOT have your system
partition on a Raid-5 disk are incorrect. 

-- 
Kevin Weilbacher [SBS-MVP]
"The days pass by so quickly now, the nights are seldom long"
"Fred Blum" <h.f.blum@marketconnectnospam.nl> wrote in message 
news:%23T4XKiE2EHA.1192@tk2msftngp13.phx.gbl...
>
> Thanks,
>
> had not thought of that and you're right. My RIAD controller doesn't allow 
> a dynamic resizing on W2K.
> IMHO opinion this thread question/answer should be in the FAQ.
>
> Fred
>
> "Joshua Bolton" <JoshuaBolton@discussions.microsoft.com> wrote in message 
> news:5AC99C16-73A5-4B52-98B6-113D9E26E73D@microsoft.com...
>> Kevin I would point out that this configuration precludes any disk space
>> being added to your system.  This is why the standard has been mirror 
>> [raid1]
>> the OS and stripe [raid 5/0+1/10] the data.
>>
>> Here is the reason why.  It is common to need to add disk space to the 
>> data
>> partition/drive.  Most raid controllers don't allow dynamic upgrades in 
>> the
>> raid array.  So to add more disk space with your present configuration 
>> you
>> have to wipe the existing array and recreate the raid5 array with the
>> additional disk so you have more space.  This usually means you have to
>> repartition the way you want, reinstall the OS and backup software and
>> restore from a backup.  A long painful process.
>>
>> Lets say you have a raid controller that can add the disk to the array
>> dynamicly.  Great.  Now you have system, apps and data partitions.  How 
>> are
>> you going to add the "unallocated space" to the data partition?  You only
>> have two options.  The best being buy a server version of Partition Magic 
>> and
>> use it to add the space to data.  Or create a volume set between the data
>> partition and the unallocated space [very bad choice since I have seen 
>> chkdsk
>> /f destroy a volume set].
>>
>> Now if you had mirrored the OS and stripped the data [in your case apps 
>> and
>> data] it is a simple matter of backup apps and data, reinit the array 
>> with
>> the added disk, use disk manager to partition as you desire and format 
>> the
>> partitions.  Then restore from backup.  I have done this in 4 hours on a 
>> Sat.
>> [depending on how long it took to init the array and restore data].
>>
>> Lets say you wanted to make the OS drive space larger.  You can't mirror 
>> to
>> a larger drive.  But you can break the mirror, use ghost to ghost from 
>> small
>> driver to larger and then with another larger drive in the system mirror 
>> the
>> two.  Again a fairly straight forward operation which you can not do if 
>> you
>> have all three partitions on a single raid5 array.  This is a two hour or
>> less operation.
>>
>> Just something to think about.
>>
>>
>>
>> "Kevin Weilbacher" wrote:
>>
>>> Fred, I know way back when it was recommended not to use raid-5 for your
>>> system partition. But I don't believe that is applicable any longer. I 
>>> know
>>> I use hardware Raid-5 for all my SBS servers without any problems. I 
>>> take my
>>> 3 or 4 drives, set them up in Raid-5, and partition them into 3 
>>> sections:
>>> system, apps, data.
>>
>
>

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