Difference between revisions of "Performance tuning"

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135 bytes added ,  20:52, 23 June 2016
m
corrected illumos whole disk logic
m (link to manual page for gnop(8); illumos not Illumos; FreeBSD not freeBSD; and working around error 404 for http://ivoras.sharanet.org/blog/tree/2011-01-01.freebsd-on-4k-sector-drives.html)
m (corrected illumos whole disk logic)
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ZFS will behave differently on different platforms when given a whole disk.
ZFS will behave differently on different platforms when given a whole disk.


On illumos, ZFS will enable the write cache on a whole disk while it will leave it set to whatever it was set on a partition. The illumos UFS driver cannot ensure integrity with the write cache enabled, so ZFS avoids enabling the write cache to avoid potentially causing corruption should a UFS filesystem occupy a partition on the disk.
On illumos, ZFS attempts to enable the write cache on a whole disk. The illumos (nee Solaris) UFS driver cannot ensure integrity with the write cache enabled, so by default Sun/Solaris systems using UFS file system for boot were shipped with drive write cache disabled (long ago, when Sun was still an independent company). For safety on illumos, if ZFS is not given the whole disk, it could be shared with UFS and thus it is not appropriate for ZFS to enable write cache.


On Linux, the Linux IO elevator is largely redundant given that ZFS has its own IO elevator, so ZFS will set the IO elevator to noop to avoid unnecessary CPU overhead.
On Linux, the Linux IO elevator is largely redundant given that ZFS has its own IO elevator, so ZFS will set the IO elevator to noop to avoid unnecessary CPU overhead.
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