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Old 08-16-2011, 09:18 AM   #1
Merlin53
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How to format a RAID-5 using 3 disks?


Hello All,

I have built a couple RAID's, but I'm uncertain of how I should format the partitions of the raid. Should I format partitions on each disk, and then add them to a raid, or should I create a raid on unformated disks and then format the raid as a partition? Does it matter, and are there performance/reliability issues? I'm creating a RAID-5 using 3 SATA disks on RHEL for user data area.

Thanks for any feedback,
Al
 
Old 08-16-2011, 09:22 AM   #2
acid_kewpie
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the disks have no format*. you create a block device, and then format that

*well not really, each disk is generally mountable, but looks like garbage on the filesystem
 
Old 08-16-2011, 09:29 AM   #3
Merlin53
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Thanks Chris,

I have formatted each disk as one huge partition each, and then created the RAID-5 with 3 disks, and then I think I have created a RAID-5 with raw disks (no partitions yet), and then formatted the RAID after it's been created. My question is which way is best? Or does it matter?
 
Old 08-16-2011, 09:39 AM   #4
acid_kewpie
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The only recommended way is to format the assembled block device. I might be wrong TBH, however I wouldnt think it would ever be seen as a "which way is best" scenario. You format /dev/md0 or whatever the resulting block device is called.

Last edited by acid_kewpie; 08-16-2011 at 09:40 AM.
 
Old 08-17-2011, 08:17 AM   #5
Reuti
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I agree with acid_kewpie.

I get in addition the feeling that partitioning and formatting are mixed up here. First you have to partition the disks, getting /dev/sda1, /dev/sdb1 and /dev/sdc1 or alike. Then assemble these partitions as mentioned to /dev/md0 building the RAID5, and then format this /dev/md0 with ext2/3/4.

I found this about the usage of a raw device without partitions, although I didnít get it working when I tried it at one time and used partitions in the end.
 
Old 08-17-2011, 08:32 AM   #6
Merlin53
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Thanks to all that replied!

I guess to be more specific I should have used the term "partition" instead of format in my original question. I plan to "Partition" each of the three disks using one primary partition, then build a RAID-5 using those disks, then I will make a file system by formatting them. That has worked before, I just wondered if there was wright/wrong way to proceed.

thanks again,
Al
 
  


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