ZFS Cache
Metadata Cache
There is a lot out there about ZFS cache config. I’ve found the most significant feature to be putting your metadata on a dedicated NVMe devices. This is noted as a ‘Special’ VDev. Here’s an example of a draid with such a device at the end.
Note: A 2x18 is bad practice - just more fun than a 3x12 with no spares.
zpool create -f pool02 \
draid3:14d:18c:1s \
ata-ST4000NM000A-2HZ100_WJG04M27 \
ata-ST4000NM000A-2HZ100_WJG09BH7 \
ata-ST4000NM000A-2HZ100_WJG0QJ7X \
ata-ST4000NM000A-2HZ100_WS20ECCD \
ata-ST4000NM000A-2HZ100_WS20ECFH \
ata-ST4000NM000A-2HZ100_WS20JXTA \
ata-ST4000NM0024-1HT178_Z4F14K76 \
ata-ST4000NM0024-1HT178_Z4F17SJK \
ata-ST4000NM0024-1HT178_Z4F17YBP \
ata-ST4000NM0024-1HT178_Z4F1BJR1 \
ata-ST4000NM002A-2HZ101_WJG0GBXB \
ata-ST4000NM002A-2HZ101_WJG11NGC \
ata-ST4000NM0035-1V4107_ZC1168N3 \
ata-ST4000NM0035-1V4107_ZC116F11 \
ata-ST4000NM0035-1V4107_ZC116MSW \
ata-ST4000NM0035-1V4107_ZC116NZM \
ata-ST4000NM0035-1V4107_ZC118WV5 \
ata-ST4000NM0035-1V4107_ZC118WW0 \
draid3:14d:18c:1s \
ata-ST4000NM0035-1V4107_ZC118X74 \
ata-ST4000NM0035-1V4107_ZC118X90 \
ata-ST4000NM0035-1V4107_ZC118XBS \
ata-ST4000NM0035-1V4107_ZC118Z23 \
ata-ST4000NM0035-1V4107_ZC11907W \
ata-ST4000NM0035-1V4107_ZC1192GG \
ata-ST4000NM0035-1V4107_ZC1195PR \
ata-ST4000NM0035-1V4107_ZC1195V5 \
ata-ST4000NM0035-1V4107_ZC1195ZJ \
ata-ST4000NM0035-1V4107_ZC11AHH9 \
ata-ST4000NM0035-1V4107_ZC11CDD0 \
ata-ST4000NM0035-1V4107_ZC11CE77 \
ata-ST4000NM0035-1V4107_ZC11CV5E \
ata-ST4000NM0035-1V4107_ZC11D2AQ \
ata-ST4000NM0035-1V4107_ZC11HRGR \
ata-ST4000NM0035-1V4107_ZC1B200R \
ata-ST4000NM0035-1V4107_ZC1CBXEH \
ata-ST4000NM0035-1V4107_ZC1DC98B \
special mirror \
ata-MICRON_M510DC_MTFDDAK960MBP_164614A1DBC4 \
ata-MICRON_M510DC_MTFDDAK960MBP_170615BD4A74
zfs set special_small_blocks=64K pool02
Metadata is stores automatically on the special device but there’s a benefit in also directing the pool to use the special vdev for small files as well.
Sources
https://forum.level1techs.com/t/zfs-metadata-special-device-z/159954
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