Hi, We are performing couple performance tests on CephFS using fio. fio is run in k8s pod and 3 pods will be up running mounting the same pvc to CephFS volume. Here is command line for random read: fio -direct=1 -iodepth=128 -rw=randread -ioengine=libaio -bs=4k -size=1G -numjobs=5 -runtime=500 -group_reporting -directory=/tmp/cache -name=Rand_Read_Testing_$BUILD_TIMESTAMP The random read is performed very slow. Here is the cluster log from dashboard: 5/30/23 8:13:16 PM [INF] Health check cleared: MDS_SLOW_REQUEST (was: 1 MDSs report slow requests) 5/30/23 8:13:16 PM [INF] Health check cleared: MDS_SLOW_METADATA_IO (was: 1 MDSs report slow metadata IOs) 5/30/23 8:13:16 PM [INF] MDS health message cleared (mds.?): 1 slow metadata IOs are blocked > 30 secs, oldest blocked for 33 secs 5/30/23 8:13:16 PM [INF] MDS health message cleared (mds.?): 1 slow requests are blocked > 30 secs 5/30/23 8:13:14 PM [WRN] Health check update: 2 MDSs report slow requests (MDS_SLOW_REQUEST) 5/30/23 8:13:13 PM [INF] MDS health message cleared (mds.?): 1 slow requests are blocked > 30 secs 5/30/23 8:13:08 PM [WRN] Health check failed: 1 MDSs report slow requests (MDS_SLOW_REQUEST) 5/30/23 8:13:08 PM [WRN] Health check failed: 1 MDSs report slow metadata IOs (MDS_SLOW_METADATA_IO) 5/30/23 8:13:08 PM [WRN] slow request 34.213327 seconds old, received at 2023-05-30T12:12:33.951399+0000: client_request(client.270564:1406144 getattr pAsLsXsFs #0x700000103d0 2023-05-30T12:12:33.947323+0000 caller_uid=0, caller_gid=0{}) currently failed to rdlock, waiting 5/30/23 8:13:08 PM [WRN] 1 slow requests, 1 included below; oldest blocked for > 34.213328 secs 5/30/23 8:13:07 PM [WRN] slow request 33.169703 seconds old, received at 2023-05-30T12:12:33.952078+0000: peer_request:client.270564:1406144 currently dispatched 5/30/23 8:13:07 PM [WRN] 1 slow requests, 1 included below; oldest blocked for > 33.169704 secs 5/30/23 8:13:04 PM [INF] Cluster is now healthy 5/30/23 8:13:04 PM [INF] Health check cleared: MDS_SLOW_REQUEST (was: 1 MDSs report slow requests) 5/30/23 8:13:04 PM [INF] Health check cleared: MDS_SLOW_METADATA_IO (was: 1 MDSs report slow metadata IOs) 5/30/23 8:13:04 PM [INF] MDS health message cleared (mds.?): 9 slow metadata IOs are blocked > 30 secs, oldest blocked for 45 secs 5/30/23 8:13:04 PM [INF] MDS health message cleared (mds.?): 2 slow requests are blocked > 30 secs 5/30/23 8:12:57 PM [WRN] 2 slow requests, 0 included below; oldest blocked for > 44.954377 secs 5/30/23 8:12:52 PM [WRN] 2 slow requests, 0 included below; oldest blocked for > 39.954313 secs 5/30/23 8:12:48 PM [WRN] Health check failed: 1 MDSs report slow requests (MDS_SLOW_REQUEST) 5/30/23 8:12:47 PM [WRN] slow request 34.935921 seconds old, received at 2023-05-30T12:12:12.185614+0000: client_request(client.270564:1406139 create #0x7000001045b/atomic7966567911433736706tmp 2023-05-30T12:12:12.182999+0000 caller_uid=0, caller_gid=0{}) currently submit entry: journal_and_reply 5/30/23 8:12:47 PM [WRN] slow request 34.954254 seconds old, received at 2023-05-30T12:12:12.167281+0000: client_request(client.270564:1406138 rename #0x70000010457/build.xml #0x70000010457/atomic6590865221269854506tmp 2023-05-30T12:12:12.162999+0000 caller_uid=0, caller_gid=0{}) currently submit entry: journal_and_reply 5/30/23 8:12:47 PM [WRN] 2 slow requests, 2 included below; oldest blocked for > 34.954254 secs 5/30/23 8:12:44 PM [WRN] Health check failed: 1 MDSs report slow metadata IOs (MDS_SLOW_METADATA_IO) 5/30/23 8:12:41 PM [INF] Cluster is now healthy 5/30/23 8:12:41 PM [INF] Health check cleared: MDS_SLOW_REQUEST (was: 1 MDSs report slow requests) 5/30/23 8:12:41 PM [INF] MDS health message cleared (mds.?): 1 slow requests are blocked > 30 secs 5/30/23 8:12:40 PM [INF] Health check cleared: MDS_SLOW_METADATA_IO (was: 1 MDSs report slow metadata IOs) 5/30/23 8:12:40 PM [INF] MDS health message cleared (mds.?): 1 slow metadata IOs are blocked > 30 secs, oldest blocked for 38 secs However, random write test is performing very good. Any suggestions on the problem? Thanks, Ben