#. A small partition is formatted with XFS and contains basic metadata
for the OSD. This *data directory* includes information about the
OSD (its identifier, which cluster it belongs to, and its private
- keyring.
+ keyring).
#. The rest of the device is normally a large partition occupying the
rest of the device that is managed directly by BlueStore contains
ceph-disk prepare --bluestore <device> --block.wal <wal-device> --block-db <db-device>
-Cache size
-==========
+Provisioning strategies
+-----------------------
+Although there are multiple ways to deploy a Bluestore OSD (unlike Filestore
+which had 1) here are two common use cases that should help clarify the
+initial deployment strategy:
+
+.. _bluestore-single-type-device-config:
+
+**block (data) only**
+^^^^^^^^^^^^^^^^^^^^^
+If all the devices are the same type, for example all are spinning drives, and
+there are no fast devices to combine these, it makes sense to just deploy with
+block only and not try to separate ``block.db`` or ``block.wal``. The
+:ref:`ceph-volume-lvm` call for a single ``/dev/sda`` device would look like::
+
+ ceph-volume lvm create --bluestore --data /dev/sda
+
+If logical volumes have already been created for each device (1 LV using 100%
+of the device), then the :ref:`ceph-volume-lvm` call for an lv named
+``ceph-vg/block-lv`` would look like::
+
+ ceph-volume lvm create --bluestore --data ceph-vg/block-lv
+
+.. _bluestore-mixed-device-config:
+
+**block and block.db**
+^^^^^^^^^^^^^^^^^^^^^^
+If there is a mix of fast and slow devices (spinning and solid state),
+it is recommended to place ``block.db`` on the faster device while ``block``
+(data) lives on the slower (spinning drive). Sizing for ``block.db`` should be
+as large as possible to avoid performance penalties otherwise. The
+``ceph-volume`` tool is currently not able to create these automatically, so
+the volume groups and logical volumes need to be created manually.
+
+For the below example, lets assume 4 spinning drives (sda, sdb, sdc, and sdd)
+and 1 solid state drive (sdx). First create the volume groups::
+
+ $ vgcreate ceph-block-0 /dev/sda
+ $ vgcreate ceph-block-1 /dev/sdb
+ $ vgcreate ceph-block-2 /dev/sdc
+ $ vgcreate ceph-block-3 /dev/sdd
+
+Now create the logical volumes for ``block``::
+
+ $ lvcreate -l 100%FREE -n block-0 ceph-block-0
+ $ lvcreate -l 100%FREE -n block-1 ceph-block-1
+ $ lvcreate -l 100%FREE -n block-2 ceph-block-2
+ $ lvcreate -l 100%FREE -n block-3 ceph-block-3
+
+We are creating 4 OSDs for the four slow spinning devices, so assuming a 200GB
+SSD in ``/dev/sdx`` we will create 4 logical volumes, each of 50GB::
+
+ $ vgcreate ceph-db-0 /dev/sdx
+ $ lvcreate -L 50GB -n db-0 ceph-db-0
+ $ lvcreate -L 50GB -n db-1 ceph-db-0
+ $ lvcreate -L 50GB -n db-2 ceph-db-0
+ $ lvcreate -L 50GB -n db-3 ceph-db-0
+
+Finally, create the 4 OSDs with ``ceph-volume``::
+
+ $ ceph-volume lvm create --bluestore --data ceph-block-0/block-0 --block.db ceph-db-0/db-0
+ $ ceph-volume lvm create --bluestore --data ceph-block-1/block-1 --block.db ceph-db-0/db-1
+ $ ceph-volume lvm create --bluestore --data ceph-block-2/block-2 --block.db ceph-db-0/db-2
+ $ ceph-volume lvm create --bluestore --data ceph-block-3/block-3 --block.db ceph-db-0/db-3
+
+These operations should end up creating 4 OSDs, with ``block`` on the slower
+spinning drives and a 50GB logical volume for each coming from the solid state
+drive.
+
+Sizing
+======
+When using a :ref:`mixed spinning and solid drive setup
+<bluestore-mixed-device-config>` it is important to make a large-enough
+``block.db`` logical volume for Bluestore. Generally, ``block.db`` should have
+*as large as possible* logical volumes.
+
+It is recommended that the ``block.db`` size isn't smaller than 4% of
+``block``. For example, if the ``block`` size is 1TB, then ``block.db``
+shouldn't be less than 40GB.
+
+If *not* using a mix of fast and slow devices, it isn't required to create
+separate logical volumes for ``block.db`` (or ``block.wal``). Bluestore will
+automatically manage these within the space of ``block``.
+
+
+Automatic Cache Sizing
+======================
+
+Bluestore can be configured to automatically resize it's caches when tc_malloc
+is configured as the memory allocator and the ``bluestore_cache_autotune``
+setting is enabled. This option is currently enabled by default. Bluestore
+will attempt to keep OSD heap memory usage under a designated target size via
+the ``osd_memory_target`` configuration option. This is a best effort
+algorithm and caches will not shrink smaller than the amount specified by
+``osd_memory_cache_min``. Cache ratios will be chosen based on a hierarchy
+of priorities. If priority information is not availabe, the
+``bluestore_cache_meta_ratio`` and ``bluestore_cache_kv_ratio`` options are
+used as fallbacks.
+
+``bluestore_cache_autotune``
+
+:Description: Automatically tune the ratios assigned to different bluestore caches while respecting minimum values.
+:Type: Boolean
+:Requered: Yes
+:Default: ``True``
+
+``osd_memory_target``
+
+:Description: When tcmalloc is available and cache autotuning is enabled, try to keep this many bytes mapped in memory. Note: This may not exactly match the RSS memory usage of the process. While the total amount of heap memory mapped by the process should generally stay close to this target, there is no guarantee that the kernel will actually reclaim memory that has been unmapped. During initial developement, it was found that some kernels result in the OSD's RSS Memory exceeding the mapped memory by up to 20%. It is hypothesised however, that the kernel generally may be more aggressive about reclaiming unmapped memory when there is a high amount of memory pressure. Your mileage may vary.
+:Type: Unsigned Integer
+:Requered: Yes
+:Default: ``4294967296``
+
+``bluestore_cache_autotune_chunk_size``
+
+:Description: The chunk size in bytes to allocate to caches when cache autotune is enabled. When the autotuner assigns memory to different caches, it will allocate memory in chunks. This is done to avoid evictions when there are minor fluctuations in the heap size or autotuned cache ratios.
+:Type: Unsigned Integer
+:Requered: No
+:Default: ``33554432``
+
+``bluestore_cache_autotune_interval``
+
+:Description: The number of seconds to wait between rebalances when cache autotune is enabled. This setting changes how quickly the ratios of the difference caches are recomputed. Note: Setting the interval too small can result in high CPU usage and lower performance.
+:Type: Float
+:Requered: No
+:Default: ``5``
+
+``osd_memory_base``
+
+:Description: When tcmalloc and cache autotuning is enabled, estimate the minimum amount of memory in bytes the OSD will need. This is used to help the autotuner estimate the expected aggregate memory consumption of the caches.
+:Type: Unsigned Interger
+:Required: No
+:Default: ``805306368``
+
+``osd_memory_expected_fragmentation``
+
+:Description: When tcmalloc and cache autotuning is enabled, estimate the percent of memory fragmentation. This is used to help the autotuner estimate the expected aggregate memory consumption of the caches.
+:Type: Float
+:Required: No
+:Default: ``0.15``
+
+``osd_memory_cache_min``
+
+:Description: When tcmalloc and cache autotuning is enabled, set the minimum amount of memory used for caches. Note: Setting this value too low can result in significant cache thrashing.
+:Type: Unsigned Integer
+:Required: No
+:Default: ``134217728``
+
+``osd_memory_cache_resize_interval``
+
+:Description: When tcmalloc and cache autotuning is enabled, wait this many seconds between resizing caches. This setting changes the total amount of memory available for bluestore to use for caching. Note: Setting the interval too small can result in memory allocator thrashing and lower performance.
+:Type: Float
+:Required: No
+:Default: ``1``
+
+
+Manual Cache Sizing
+===================
The amount of memory consumed by each OSD for BlueStore's cache is
determined by the ``bluestore_cache_size`` configuration option. If
* BlueStore data (i.e., recently read or written object data)
Cache memory usage is governed by the following options:
-``bluestore_cache_meta_ratio``, ``bluestore_cache_kv_ratio``, and
-``bluestore_cache_kv_max``. The fraction of the cache devoted to data
-is 1.0 minus the meta and kv ratios. The memory devoted to kv
-metadata (the RocksDB cache) is capped by ``bluestore_cache_kv_max``
-since our testing indicates there are diminishing returns beyond a
-certain point.
+``bluestore_cache_meta_ratio`` and ``bluestore_cache_kv_ratio``.
+The fraction of the cache devoted to data
+is governed by the effective bluestore cache size (depending on
+``bluestore_cache_size[_ssd|_hdd]`` settings and the device class of the primary
+device) as well as the meta and kv ratios.
+The data fraction can be calculated by
+``<effective_cache_size> * (1 - bluestore_cache_meta_ratio - bluestore_cache_kv_ratio)``
``bluestore_cache_size``
:Description: The ratio of cache devoted to metadata.
:Type: Floating point
:Required: Yes
-:Default: ``.01``
+:Default: ``.4``
``bluestore_cache_kv_ratio``
:Description: The ratio of cache devoted to key/value data (rocksdb).
:Type: Floating point
:Required: Yes
-:Default: ``.99``
+:Default: ``.4``
``bluestore_cache_kv_max``
It is possible to use a smaller checksum value by truncating the
checksum to two or one byte, reducing the metadata overhead. The
trade-off is that the probability that a random error will not be
-detected is higher with a smaller checksum, going from about one if
-four billion with a 32-bit (4 byte) checksum to one is 65,536 for a
+detected is higher with a smaller checksum, going from about one in
+four billion with a 32-bit (4 byte) checksum to one in 65,536 for a
16-bit (2 byte) checksum or one in 256 for an 8-bit (1 byte) checksum.
The smaller checksum values can be used by selecting `crc32c_16` or
`crc32c_8` as the checksum algorithm.
projects / ceph.git / blobdiff