We are benchmarking a test machine which has: 8 cores, 64GB RAM 12 * 12 TB HDD (SATA) 2 * 480 GB SSD (SATA) 1 * 240 GB SSD (NVME) Ceph Mimic
Baseline benchmark for HDD only (Erasure Code 4+2) Write 420 MB/s, 100 IOPS, 150ms latency Read 1040 MB/s, 260 IOPS, 60ms latency Now we moved WAL to the SSD (all 12 WALs on single SSD, default size (512MB)): Write 640 MB/s, 160 IOPS, 100ms latency Read identical as above. Nice boost we thought, so we moved WAL+DB to the SSD (Assigned 30GB for DB) All results are the same as above! Q: This is suspicious, right? Why is the DB on SSD not helping with our benchmark? We use *rados bench* We tried putting WAL on the NVME, and again, the results are the same as on SSD. Same for WAL+DB on NVME Again, the same speed. Any ideas why we don't gain speed by using faster HW here? Jan -- Jan Senko, Skype janos- Phone in Switzerland: +41 774 144 602 Phone in Czech Republic: +420 777 843 818
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