Month: February 2022

This is much better than the Samsung 980 NVME SSD. The settings i used.

fio --filename=/dev/nvme0n1 --direct=1 --rw=write --bs=4k --ioengine=libaio --iodepth=1 --runtime=10 --numjobs=1 --time_based --group_reporting --name=iops-test-job --sync=1

I used Ceph blockdb and wal cache before. It did not do any read caching. Lvm caching is smarter. It caches the most used blocks. When i start up something it can be slow at first, but after a while the read and write speeds go up. I set caching mode to writeback. I used cachepool and not cachevol.

• Create a PV of the SSD
• Add PV to same VG as the slow HDD
• Create a large cache LV on the SSD
• Create a smaller metadata cache LV on the SSD
• Create cache LV from data and metadata LV
• Add cache LV to the HDD LV

Everything can be done while the HDD LV is online.

I tested a new one i bought a few days ago. I tested with fio. I set sync=1, direct=1, blocksize=4k, iodepth=1 and numjobs=1