mirror of
https://github.com/ceph/ceph
synced 2024-12-21 10:54:42 +00:00
86 lines
3.8 KiB
ReStructuredText
86 lines
3.8 KiB
ReStructuredText
===========================================
|
|
Hard Disk and File System Recommendations
|
|
===========================================
|
|
|
|
.. index:: hard drive preparation
|
|
|
|
Hard Drive Prep
|
|
===============
|
|
|
|
Ceph aims for data safety, which means that when the :term:`Ceph Client`
|
|
receives notice that data was written to a storage drive, that data was actually
|
|
written to the storage drive. For old kernels (<2.6.33), disable the write cache
|
|
if the journal is on a raw drive. Newer kernels should work fine.
|
|
|
|
Use ``hdparm`` to disable write caching on the hard disk::
|
|
|
|
sudo hdparm -W 0 /dev/hda 0
|
|
|
|
In production environments, we recommend running a :term:`Ceph OSD Daemon` with
|
|
separate drives for the operating system and the data. If you run data and an
|
|
operating system on a single disk, we recommend creating a separate partition
|
|
for your data.
|
|
|
|
.. index:: filesystems
|
|
|
|
Filesystems
|
|
===========
|
|
|
|
Ceph OSD Daemons rely heavily upon the stability and performance of the
|
|
underlying filesystem.
|
|
|
|
.. note:: We currently recommend ``XFS`` for production deployments.
|
|
We recommend ``btrfs`` for testing, development, and any
|
|
non-critical deployments. We believe that ``btrfs`` has the correct
|
|
feature set and roadmap to serve Ceph in the long-term, but ``XFS``
|
|
and ``ext4`` provide the necessary stability for today's deployments.
|
|
``btrfs`` development is proceeding rapidly: users should be
|
|
comfortable installing the latest released upstream kernels and be
|
|
able to track development activity for critical bug fixes.
|
|
|
|
Ceph OSD Daemons depend on the Extended Attributes (XATTRs) of the underlying
|
|
file system for various forms of internal object state and metadata. The
|
|
underlying filesystem must provide sufficient capacity for XATTRs. ``btrfs``
|
|
does not bound the total xattr metadata stored with a file. ``XFS`` has a
|
|
relatively large limit (64 KB) that most deployments won't encounter, but the
|
|
``ext4`` is too small to be usable.
|
|
|
|
You should always add the following line to the ``[osd]`` section of your
|
|
``ceph.conf`` file for ``ext4`` filesystems; you can optionally use
|
|
it for ``btrfs`` and ``XFS``.::
|
|
|
|
filestore xattr use omap = true
|
|
|
|
|
|
Filesystem Background Info
|
|
==========================
|
|
|
|
The ``XFS``, ``btrfs`` and ``ext4`` file systems provide numerous advantages in highly
|
|
scaled data storage environments when `compared`_ to ``ext3``.
|
|
|
|
``XFS``, ``btrfs`` and ``ext4`` are `journaling file systems`_, which means that
|
|
they are more robust when recovering from crashes, power outages, etc. These
|
|
filesystems journal all of the changes they will make before performing writes.
|
|
|
|
``XFS`` was developed for Silicon Graphics, and is a mature and stable
|
|
filesystem. By contrast, ``btrfs`` is a relatively new file system that aims
|
|
to address the long-standing wishes of system administrators working with
|
|
large scale data storage environments. ``btrfs`` has some unique features
|
|
and advantages compared to other Linux filesystems.
|
|
|
|
``btrfs`` is a `copy-on-write`_ filesystem. It supports file creation
|
|
timestamps and checksums that verify metadata integrity, so it can detect
|
|
bad copies of data and fix them with the good copies. The copy-on-write
|
|
capability means that ``btrfs`` can support snapshots that are writable.
|
|
``btrfs`` supports transparent compression and other features.
|
|
|
|
``btrfs`` also incorporates multi-device management into the file system,
|
|
which enables you to support heterogeneous disk storage infrastructure,
|
|
data allocation policies. The community also aims to provide ``fsck``,
|
|
deduplication, and data encryption support in the future. This compelling
|
|
list of features makes ``btrfs`` the ideal choice for Ceph clusters.
|
|
|
|
.. _copy-on-write: http://en.wikipedia.org/wiki/Copy-on-write
|
|
.. _compared: http://en.wikipedia.org/wiki/Comparison_of_file_systems
|
|
.. _journaling file systems: http://en.wikipedia.org/wiki/Journaling_file_system
|