From: Sridhar Seshasayee Date: Fri, 16 Jun 2023 07:44:09 +0000 (+0530) Subject: Merge pull request #51978 from sseshasa/wip-61624-quincy X-Git-Tag: v17.2.7~293 X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=c0c1382c4c244f080a2bf021b4b0fa3350cd0592;p=ceph.git Merge pull request #51978 from sseshasa/wip-61624-quincy quincy: PendingReleaseNotes: Document mClock scheduler fixes and enhancements Reviewed-by: Neha Ojha --- c0c1382c4c244f080a2bf021b4b0fa3350cd0592 diff --cc PendingReleaseNotes index 6d576173b1ea,58b37672d686..cbdc83fc8a28 --- a/PendingReleaseNotes +++ b/PendingReleaseNotes @@@ -5,10 -5,30 +5,33 @@@ registered a RADOS client in the `name` field added to elements of the `active_clients` array. Previously, only the address of a module's RADOS client was shown in the `active_clients` array. + * mClock Scheduler: The mClock scheduler (default scheduler in Quincy) has + undergone significant usability and design improvements to address the slow + backfill issue. Some important changes are: + * The 'balanced' profile is set as the default mClock profile because it + represents a compromise between prioritizing client IO or recovery IO. Users + can then choose either the 'high_client_ops' profile to prioritize client IO + or the 'high_recovery_ops' profile to prioritize recovery IO. + * QoS parameters like reservation and limit are now specified in terms of a + fraction (range: 0.0 to 1.0) of the OSD's IOPS capacity. + * The cost parameters (osd_mclock_cost_per_io_usec_* and + osd_mclock_cost_per_byte_usec_*) have been removed. The cost of an operation + is now determined using the random IOPS and maximum sequential bandwidth + capability of the OSD's underlying device. + * Degraded object recovery is given higher priority when compared to misplaced + object recovery because degraded objects present a data safety issue not + present with objects that are merely misplaced. Therefore, backfilling + operations with the 'balanced' and 'high_client_ops' mClock profiles may + progress slower than what was seen with the 'WeightedPriorityQueue' (WPQ) + scheduler. + * The QoS allocations in all the mClock profiles are optimized based on the above + fixes and enhancements. + * For more detailed information see: + https://docs.ceph.com/en/quincy/rados/configuration/mclock-config-ref/ +* CEPHFS: After recovering a Ceph File System post following the disaster recovery + procedure, the recovered files under `lost+found` directory can now be deleted. + >=17.2.6 --------