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Old 03-01-2015, 05:05 PM   #1
wtdedula
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Question about a=setting up a RAID array using mdadm


Hi All;
I am new to Linux and Ubuntu. I am setting up a RAID for a media server and want to be sure I do it right and in the proper order.

Based upon feedback received on this forum I think it makes most sense to partition my 4 TB disks into 2 partitions of 2 TB each.

So am I correct in running MDADM FIRST on both (Unpartitioned) 4 TB disks to create RAID 1 and then partition (Using Parted) the resulting single 4 TB disk that I create with MDADM into two 2 TB partitions? Thanks.

Tim
 
Old 03-01-2015, 06:07 PM   #2
jlinkels
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The common way is to first partition and then RAID each partition.

So in your case you could create 2 partitions on /dev/sda, and 2 on /dev/sdb. Then you RAID /dev/sda1 with /dev/sdb1 and /dev/sda2 with /dev/sdb2.

What you propose would also work, but generally it is done like descibed above.

jlinkels
 
Old 03-01-2015, 06:23 PM   #3
syg00
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Before you start, it might be worth bookmarking the Linux_Raid Wiki site.

Is this just for media (not "system") content ?. If so, why do you envisage needing two partitions on each disk ?.
 
Old 03-01-2015, 06:54 PM   #4
wtdedula
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Hi All;
Thanks for your helpful responses.

Here is more information -
My system disk is sda and I believe that is a 128 GB SSD.
I have two large disks (sdb and sdc) to hold content (video, audio, etc). It is these two disks that I want to create RAID 1 from.

syg00 - I was originally going to only create one 4TB partition per disk since I know it is capable using gpt but feedback received from in this forum about a week ago seemed to imply that a 4 TB [partition is too large and I should at least have several partitions. How many partitions do you suggest I create, syg00?

Jlinkles - what you said makes perfect sense.

Thanks for your continued feedback - I am learning so much :-).

Tim
 
Old 03-01-2015, 07:22 PM   #5
syg00
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Hmm - looks like I was in that thread too.
The assertion for 4 partitions was made by one respondent without knowing your intended usage, and without any reasoning.

No intrinsic reason to use more than one partition (using parted is fine), then create the RAID1 device across those.
You could also use the raw devices unpartitioned, but use what you are comfortable with - some people find unpartitioned devices confusing. Have a look at the wiki.
 
Old 03-01-2015, 07:49 PM   #6
wtdedula
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syg00;
Thanks for your insight. Makes sense to me though I think you're right in that I would be confused by unpartitioned drives. I would be nervous doing it that way. I did bookmark the wiki and will take a look at it some tonight and tomorrow before I create the RAID.

Tim
 
Old 03-01-2015, 08:09 PM   #7
syg00
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I trust you are aware RAID doesn't obviate the need for (good) backups. Depending on the value you ascribe to your collection ...
 
Old 03-02-2015, 05:00 AM   #8
wtdedula
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syg00;
Hmmm ... I didn't know that but now that you mentioned it, I'll keep that in mind. Yes the data is valuable due to the enormous time it would take to recreate it, and some may not be available months or years after initially storing it. I'll get an external 4 TB drive to back up the data. Thanks so much.

Tim
 
  


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