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This ensures that we don't accumulate checksum errors against offline or
unavailable devices but, more importantly, means that we don't
needlessly create DTL entries for offline devices that are already
up-to-date.
Consider a 3-way mirror, with disk A always online (and so always with
an empty DTL) and B and C only occasionally online. When A & B resilver
with C offline, B's DTL will effectively be appended to C's due to these
spurious ZIOs even as the resilver empties B's DTL:
* These ZIOs land in vdev_mirror_scrub_done() and flag an error
* That flagged error causes vdev_mirror_io_done() to see
unexpected_errors, so it issues a ZIO_TYPE_WRITE repair ZIO, which
inherits ZIO_FLAG_SCAN_THREAD because zio_vdev_child_io() includes
that flag in ZIO_VDEV_CHILD_FLAGS.
* That ZIO fails, too, and eventually zio_done() gets its hands on it
and calls vdev_stat_update().
* vdev_stat_update() sees the error and this zio...
* is not speculative,
* is not due to EIO (but rather ENXIO, since the device is closed)
* has an ->io_vd != NULL (specifically, the offline leaf device)
* is a write
* is for a txg != 0 (but rather the read block's physical birth txg)
* has ZIO_FLAG_SCAN_THREAD asserted
* So: vdev_stat_update() calls vdev_dtl_dirty() on the offline vdev.
Then, when A & C resilver with B offline, that story gets replayed and
C's DTL will be appended to B's.
In fact, one does not need this permanently-broken-mirror scenario to
induce badness: breaking a mirror with no DTLs and then scrubbing will
create DTLs for all offline devices. These DTLs will persist until the
entire mirror is reassembled for the duration of the *resilver*, which,
incidentally, will not consider the devices with good data to be sources
of good data in the case of a read failure.
Reviewed-by: Mark Maybee <mark.maybee@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Nathaniel Wesley Filardo <nwfilardo@gmail.com>
Closes #11930
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| zfs.release.in | ||
OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.
Official Resources
- Documentation - for using and developing this repo
- ZoL Site - Linux release info & links
- Mailing lists
- OpenZFS site - for conference videos and info on other platforms (illumos, OSX, Windows, etc)
Installation
Full documentation for installing OpenZFS on your favorite operating system can be found at the Getting Started Page.
Contribute & Develop
We have a separate document with contribution guidelines.
We have a Code of Conduct.
Release
OpenZFS is released under a CDDL license.
For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197
Supported Kernels
- The
METAfile contains the officially recognized supported Linux kernel versions. - Supported FreeBSD versions are any supported branches and releases starting from 12.2-RELEASE.