Skip to main content

Dmitry Serebrennikov

Dmitry Serebrennikov's Public Library

  • ashift: Can only be set at pool creation time. Pool sector size exponent, to the power of 2. I/O operations will be aligned to the specified size boundaries. Default value is "9", as 2^9 = 512, the standard sector size operating system utilities use for reading and writing data. For advanced format drives with 4 KiB boundaries, the value should be set to "ashift=12", as 2^12 = 4096.
    • autoexpand: Must be set before replacing the first drive in your pool. Controls automatic pool expansion when the underlying LUN is grown. Default is "off". After all drives in the pool have been replaced with larger drives, the pool will automatically grow to the new size. This setting is a boolean, with values either "on" or "off".

    • If using a hybrid storage pool with multiple devices, mirror the SLOG and stripe the L2ARC.
  • When using advanced format disks that read and write data in 4 KB sectors, set the "ashift" value to 12 on pool creation for maximum performance. Default is 9 for 512-byte sectors.
  • GlusterFS, Ceph, Lustre

  • Second, various drives will be implemented with different nanometer processes. The smaller the nanometer process, the shorter the life of your SSD. As an example, the Intel 320 is a 25 nanometer MLC 300 GB SSD, and is rated at roughly 5000 P/E cycles. This means you can write to your entire SSD 5000 times if using wear leveling algorithms. This produces 1500000 GB of total written data, or 1500 TB. My ZIL maintains about 3 MB of data per second. As a result, I can maintain about 95 TB of written data per year. This gives me a life of about 15 years for this Intel SSD.


    However, the Intel 335 is a 20 nanometer MLC 240 GB SSD, and is rated at roughly 3000 P/E cycles. With wear leveling, this means you can write you entire SSD 3000 times, which produces 720 TB of total written data. This is only 7 years for my 3 MBps ZIL, which is less than 1/2 the life expectancy the Intel 320. Point is, you need to keep an eye on these things when planning out your pool.

1 - 20 of 2169 Next › Last »
20 items/page

Highlighter, Sticky notes, Tagging, Groups and Network: integrated suite dramatically boosting research productivity. Learn more »

Join Diigo