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ewwhite
Asked: 2011-05-25 14:59:24 +0800 CST

ZFS (NexentaStor) and 4k Advanced Format Partition Alignment

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I have a storage system that contains 8 x 1TB drives that use the 4k sector size "Advanced Format". I'm planning to run NexentaStor on this hardware and want to ensure that I'm taking the 4k sector size into account. Is there anything special I need to keep in mind when creating the root pool and subsequent data pools with ZFS?

zfs advanced-format nexenta

1 Answers

  1. Best Answer

    ZFS handles 4k sectors well as long as the drive advertises them correctly.

    However, some drives have 4k sectors internally but present a logical 512 sector size to the operating system for backwards compatibility. If ZFS believes the drive, and writes in 512 byte chunks to 4k sectors, you'll suffer a heavy read-modify-write penalty.

    Have a look at the Solarismen blog:

    If your drive reports a sector size of 4k, you're fine. If your drive reports a sector size of 512, you may be able to work around it by using the modified zpool binary from the same site:

    The modified binary hardcodes the sector size to 4k. Note that you only need to use it for the initial zpool creation. This may be a bit difficult for your root pool - you may need to slipstream the modified binary in to the NexentaStor ISO.

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