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Learning Ceph - Second Edition by Karan Singh, Vaibhav Bhembre, Anthony D'Atri

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Client settings

Ceph's RBD block service is heavily utilized by cloud platforms like OpenStack and other virtualization solutions. Effective caching in memory on the client side can significantly improve the performance that users experience:

[client.yourclientname]rbd_cache = truerbd_cache_size = 67108864rbd_cache_max_dirty = 50331648rbd_cache_target_dirty = 33554432

These values of 64MB, 48MB, and 32MB are double the default numerical values as of Luminous.

Settings must be selected so that rbd_cache_size > rbd_cache_max_dirty > rbd_cache_target_dirty.

Some references suggest larger values, but consider that these cache buffers are allocated per attached volume. Consider a dense hypervisor node hosting 100 smaller VM instances, each mapping ...

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