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I'm getting confused by this "Advanced Format" (4KB sectors) talk of bigger (2TB) drives - and I am wondering about how I would resolve this if I'm building a new software (mdadm) RAID-5 array.

The drives I'm gonna buy is the Western Digitial Caviar® Green 2TB, 64MB cache. And probably 4, or maybe 6, of these to make me a new RAID5 storage.

With my older setup, 6x500GB drives in RAID-5, I included the whole drives (/dev/sda, /dev/sdb ..) without any partition-table, and then made the ext4-fs on the whole raid /dev/md0 without any partition-table.

But with this "Advanced Format" thingie, I'm wondering if I have to make a GPT-partition-table on these 2TB-drives, with a 1024kb offset(?), include the partitions in a RAID-5 array, and then also make a GPT-partition-table before making the file system? Is this necessary to get good speed from the array? Or could I use the old way of doing it, without noticing any difference?

Also... Is there any parameters I should be aware of while making the RAID-5 by mdadm to get the best speed? (In regard to the 4GB sectors of the drives). And also, should I format this storage with any special parameters? I'm planning on building an EXT-4 filesystem.

Sorry for this confused post, but I'm pretty confused myself of what this "Advanced Format" is and how this would impact my planned RAID-setup.

EDIT: And also... Any advice on the RAID5 chunk size I should use?

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  • Not a solution, but you really shouldn't be using RAID-5 with multi-terabyte drives. You're quite likely to have a failure during rebuild, see zdnet.com/blog/storage/why-raid-5-stops-working-in-2009/162. With drives as cheap as they are, using RAID-10 is far safer (and performs much better for writes).
    – rmalayter
    Commented Sep 20, 2010 at 13:22
  • Thanks for the input, rmalayter. Altough, I should note, this raid is primarily beeing read from - not that much writes. But I will check out that URL. :) The rebuild of my 6x500GB raid-5 did take some time, but never had any real trouble.
    – jorno
    Commented Sep 20, 2010 at 13:53

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I just did the same thing a few weeks ago.

I like the idea of the WD Green 2TB drive, but NewEgg got a batch that had a 50% failure rate. Check the user comments. I went with Seagate 2TB drives.

I had no problem making the partitions like normal, making the raid 5, building the LVM on them, and formatting it XFS.

You may want to look into XFS over ext4 for larger drives. According to the docs, XFS handles larger TB drives better then ext4.

This is on a Slackware 13.1 box. The OS is not on the huge raid 5, but on a raid 1 with smaller drives.

It all worked perfect for me.

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  • As long as you're using a fairly recent kernel, it should support the 4KB sectors without manual intervention.
    – Chris S
    Commented Sep 20, 2010 at 17:02

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