Lutz Schumann
2010-May-12 14:39 UTC
[zfs-discuss] ZIL Ramdisk Tests and very poor OpenSolaris Ramdisk Performance
Hello, probably a lot of people have done this, now its my time. I wanted to test the performance of comstar over 8 GB FC. My Idea was to create a pool from a ramdisk, a thin provisioned zvol over it and so some benchmarks. However performance is worse then to the disk backend. So I measured the ramdisk performance on opensolaris (build 134): -- a) OK whats the max we can do: root at nexenta3:/volumes# dd if=/dev/zero of=/dev/null bs=8k ^C980922+0 records in 980922+0 records out 8035713024 bytes (8.0 GB) copied, 1.58065 seconds, 5.1 GB/s Thats ok. b) What can we do reqading from the ramdisk root at nexenta3:/volumes# dd if=/dev/ramdisk/ramdisk of=/dev/null bs=8k ^C297020+0 records in 297019+0 records out 2433179648 bytes (2.4 GB) copied, 2.79683 seconds, 870 MB/s Looks ok c) Ok what can we do writing to the ramdisk ? root at nexenta3:/volumes# dd if=/dev/zero of=/dev/ramdisk/ramdisk bs=8k ^C71188+0 records in 71188+0 records out 583172096 bytes (583 MB) copied, 1.99645 seconds, 292 MB/s Whats that ?? 300 MB to memory ? Any Tips why the ramdisk performance is so bad ? --- Regards, Robert -- This message posted from opensolaris.org