Solaris 11.2 released

After a short public beta phase, Oracle made Solaris 11.2 generally available last week. You can download it from in various forms like the usual install ISO, Unified Archives and as Virtual box appliance.

There are many, many new features, but also a lot of small incremental improvements.

Some of the new key features are:

  • Openstack
  • Kernel zones
  • Puppet
  • Unified Archives
  • Elastic Virtual Switch

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Control the size of the ZFS ARC cache dynamically

Last updated on: 25th Dec 2014

Solaris 11.2 deprecates the zfs_arc_max kernel parameter in favor of user_reserve_hint_pct and that’s cool.

ZFS has a very smart cache, the so called ARC (Adaptive replacement cache). In general the ARC consumes as much memory as it is available, it also takes care that it frees up memory if other applications need more.

In theory, this works very good, ZFS just uses available memory to speed up slow disk I/O. But it also has some side effects, if the ARC consumed almost all unused memory. Applications which request more memory need to wait, until the ARC frees up memory. For example, if you restart a big database, the startup is maybe significantly delayed, because the ARC could have used the free memory from the database shutdown in the meantime already. Additionally this database would likely request large memory pages, if ARC uses just some free segments, the memory gets easily fragmented.

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