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Crimson Rider
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PostPosted: Mon Nov 21, 2005 9:22 am    Post subject: A RAID question, is this config ok? Reply with quote

Hey guys, just some simple RAID questions here, if anyone would like to comment.

I have a system with 6 SATA disks, with this system I want to muck around with RAID-5 a bit. I was thinking of making an array with 5 disks and 1 spare disk. This is the config file I've come up with

Code:
raiddev /dev/md0
        raid-level              5
        nr-raid-disks           5
        nr-spare-disks          1

        persistent-superblock   1
        parity-algorithm        left-symmetric

        chunk-size              32

        device          /dev/hde1
        raid-disk       0

        device          /dev/hdg1
        raid-disk       1

        device          /dev/hdi1
        raid-disk       2

        device          /dev/hdk1
        raid-disk       3

        device          /dev/hdm1
        raid-disk       4

        device          /dev/hdo1
        spare-disk      0


Almost verbatim from the RAID-howto, does it seem ok? Are there any obvious pitfalls I just walked into?

Also, what I couldn't find in the howto was why I would choose left-symmetric parity or a persistent superblock, I am doing some searching now, but if someone could tell me right of the bat what it is and why, I would appreciate it.

Thanx in advance.
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colo
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PostPosted: Mon Nov 21, 2005 10:05 am    Post subject: Reply with quote

Your posting suggests you're using raidtools, which are quasi depreacted. You might want to try mdadm, an all-in-onde md-config tool without the need of a config-file.

Apart from this little issue, there's nothing to be re-adjusted here, I'd say :)
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Crimson Rider
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PostPosted: Mon Nov 21, 2005 10:06 am    Post subject: Reply with quote

Some additional questions.

Should I use /dev/hde1 or is it better to use /dev/hde without a partition on the disk, ie use it raw?
I have build the array, and make a partition on it, /dev/md0p1, but nowhere is this partition found, what do I need to do to use the partition?

Thanx
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Crimson Rider
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PostPosted: Mon Nov 21, 2005 10:15 am    Post subject: Reply with quote

Thank you for the answer.

Why would I want to use mdadm? I've emerged it, and as far as I can tell, there isn't a central place where I can look up my config once I've made it.
Are there any other advantages? Or is there a reason I would not want to use a config file?

thanx
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colo
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PostPosted: Mon Nov 21, 2005 2:25 pm    Post subject: Reply with quote

I prefer RAID-levels defineable on a per-partition basis, rather than per-disk. Besides, GRUB can't boot off a raid5-volume, i suppose.

mdadm is the swiss army knife for your RAID-stuff - it's one tool to bind them all, if you get me ;) It's also great if you happen to have to recover your array from a place or system where your /etc/raidconf is not available. Plus, it's more actively developed.
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