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Some disks with internal sectors larger than 512 bytes (e.g., 4k) can suffer from bad write performance when ashift is not configured correctly. This is caused by the disk not reporting its actual sector size, but a sector size of 512 bytes. The drive may behave this way for compatibility reasons. For example, the WDC WD20EARS disks are known to exhibit this behavior. When creating a zpool, ZFS takes that wrong sector size and sets the "ashift" property accordingly (to 9: 1<<9=512), whereas it should be set to 12 for 4k sectors (1<<12=4096). This patch allows an adminstrator to manual specify the known correct ashift size at 'zpool create' time. This can significantly improve performance in certain cases. However, it will have an impact on your total pool capacity. See the updated ashift property description in the zpool.8 man page for additional details. Valid values for the ashift property range from 9 to 17 (512B-128KB). Additionally, you may set the ashift to 0 if you wish to auto-detect the sector size based on what the disk reports, this is the default behavior. The most common ashift values are 9 and 12. Example: zpool create -o ashift=12 tank raidz2 sda sdb sdc sdd Closes #280 Original-patch-by: Richard Laager <rlaager@wiktel.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
40 lines
1.6 KiB
Plaintext
40 lines
1.6 KiB
Plaintext
Brian Behlendorf is the principle developer of the ZFS on Linux port.
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He works full time as a computer scientist at Lawrence Livermore
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National Laboratory on the ZFS and Lustre filesystems. However,
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this port would not have been possible without the help of many
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others who have contributed their time, effort, and insight.
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Brian Behlendorf <behlendorf1@llnl.gov>
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First and foremost the hard working ZFS developers at Sun/Oracle.
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They are responsible for the bulk of the code in this project and
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without their efforts there never would have been a ZFS filesystem.
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The ZFS Development Team at Sun/Oracle
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Next all the developers at KQ Infotech who implemented a working
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ZFS Posix Layer (ZPL) for this port. Their implementation provided
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an excellent reference for adding the missing ZPL functionality.
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Anand Mitra <mitra@kqinfotech.com>
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Anurag Agarwal <anurag@kqinfotech.com>
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Neependra Khare <neependra@kqinfotech.com>
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Prasad Joshi <prasad@kqinfotech.com>
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Rohan Puri <rohan@kqinfotech.com>
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Sandip Divekar <sandipd@kqinfotech.com>
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Shoaib <shoaib@kqinfotech.com>
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Shrirang <shrirang@kqinfotech.com>
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Additionally the following individuals have all made contributions
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to the project and deserve to be acknowledged.
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Ricardo M. Correia <Ricardo.M.Correia@sun.com>
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Ned Bass <bass6@llnl.gov>
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Herb Wartens <wartens2@llnl.gov>
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Jim Garlick <garlick@llnl.gov>
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Manuel Amador (Rudd-O) <rudd-o@rudd-o.com>
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Gunnar Beutner <gunnar@beutner.name>
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Darik Horn <dajhorn@vanadac.com>
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Richard Laager <rlaager@wiktel.com>
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Christian Kohlschütter <christian@kohlschutter.com>
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