Materials

Method

First, the bash script above creates zfs vdevs of a certain size, ashift, volblocksize and strategy (raidz1, raidz2, raidz3, mirror and so on). Second it starts fio with a number of parameters and repeats this 5 times. Third, results are collected in a .csv file for analysis.

Because of the time involved to perform adequate random IOPS tests on ZFS, only sequential read/write benchmarks are covered here. Random IOPS benchmarks can be found there

In Open Office, each set of 5 measurements was averaged. For writing, the first result of 5 was omited as an outlier and the remaining 4 measurements were averaged. In some charts, because of jitter, the standard deviation for writing is given with an errorbar.

The results are adjusted for data disks, so for example a raidz1 of 5 disks will appear as 4 data disks in the charts.

The y-axis show scaling instead of throughput, to make the results less machine specific. Scaling means: how much better relative to a single disk does it perform. For example, a 4-disk stripe should perform 4x better than a single disk.

Raw data

The resulting .csv data sits here (5 MB). The Open Office version with aggregated results is there (2 MB)

This is the data file for gnuplot, made from the .ods file, and that is the file you can load in gnuplot to have the scaling graphs in PNG format.


Sequential read/write scaling comparison

Zpool created with -o ashift=12 -o volblocksize=64k -o primarycache=metadata.

Mdraid array with mdadm and --chunk=512 and after creation echo 8192 > /sys/block/md0/md/stripe_cache_size

ZFS stripe, how much do other volblocksizes matter?

Raidz1, how much do other volblocksizes matter?

Raidz2, how much do other volblocksizes matter?

Raidz3, how much do other volblocksizes matter?

How much does checksum=off improve performance?

Comparison of 8 disk zfs stripe, checksum=off|on

How do different striping configurations compare?

A quick test with volblocksize=64k.