Hi! I understand that this question is not quite for this mailing list, but nonetheless, experts who may be encountered this have gathered here. I have 24 servers, and on each, after six months of work, the following began to happen: [root@S-26-5-1-2 cph]# uname -a Linux S-26-5-1-2 5.2.11-1.el7.elrepo.x86_64 #1 SMP Thu Aug 29 08:10:52 EDT 2019 x86_64 x86_64 x86_64 GNU/Linux [root@S-26-5-1-2 cph]# dd if=/dev/zero of=/dev/sdc bs=1M count=1000 oflag=sync 1048576000 bytes (1.0 GB) copied, 3.76334 s, 279 MB/s [root@S-26-5-1-2 cph]# dd if=/dev/zero of=/dev/sdd bs=1M count=1000 oflag=sync 1048576000 bytes (1.0 GB) copied, 4.54834 s, 231 MB/s sdc - SSD disk. sdd - HDD. It can be seen that ssd works somehow slowly, and hdd - too quickly. Reboot - nothing changes. And only poweroff/poweron cycle change behavior to normal: [root@S-26-5-1-2 cph]# dd if=/dev/zero of=/dev/sdc bs=1M count=1000 oflag=sync 1048576000 bytes (1.0 GB) copied, 3.24042 s, 324 MB/s [root@S-26-5-1-2 cph]# dd if=/dev/zero of=/dev/sdd bs=1M count=1000 oflag=sync 1048576000 bytes (1.0 GB) copied, 13.7709 s, 76.1 MB/s Absoluteli nothing in system and ceph log (this servers used for OSD) about that. Perhaps someone has encountered similar behavior? WBR, Fyodor.