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

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

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?

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.

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 didn’t get it working when I tried it at one time and used partitions in the end.

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