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linux:fs:zfs:tuning [2025/03/04 15:17] – niziaklinux:fs:zfs:tuning [2025/08/23 08:45] (current) – niziak
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 ====== ZFS performance tuning tips ====== ====== ZFS performance tuning tips ======
 +
 +Copy-paste snippet:
 +<code bash>
 +zfs set recordsize=1M hddpool
 +zfs set recordsize=1M nvmpool
 +zfs set compression=zstd hddpool
 +zfs set compression=zstd nvmpool
 +</code>
  
 ===== zil limit ===== ===== zil limit =====
  
 ZFS parameter [[https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Module%20Parameters.html#zil-slog-bulk|zil_slog_bulk]] is responsible to ''throttle'' LOG device load. In older ZFS valu was set to 768kB, currently it is 64MB. All sync write requests above this size will be treated as async requests and written directly to slower main device. ZFS parameter [[https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Module%20Parameters.html#zil-slog-bulk|zil_slog_bulk]] is responsible to ''throttle'' LOG device load. In older ZFS valu was set to 768kB, currently it is 64MB. All sync write requests above this size will be treated as async requests and written directly to slower main device.
 +
 +<file ini /etc/modprobe.d/zfs.conf>
 +options zfs zil_slog_bulk=67108864
 +options zfs l2arc_write_max=67108864
 +</file>
  
 See similar for L2ARC: [[https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Module%20Parameters.html#l2arc-write-max|l2arc_write_max]] See similar for L2ARC: [[https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Module%20Parameters.html#l2arc-write-max|l2arc_write_max]]
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   * less metadata   * less metadata
   * less fragmentation   * less fragmentation
-  * zvol: huge overhead if guest is using small block sizes+  * zvol: huge overhead if guest is using small block sizes - try to match guest FS block size to volblock - do not set 4kB volblock size !
  
 Note: ''recordsize''  / ''volblocksize''  only defines upper limit. Smaller data still can create smaller recordsize (is it true for block?). Note: ''recordsize''  / ''volblocksize''  only defines upper limit. Smaller data still can create smaller recordsize (is it true for block?).
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 <code bash> <code bash>
 zpool iostat -r zpool iostat -r
 +
  
 </code> </code>
 +
 +===== zvol for guest =====
 +
 +  * match volblock size to guest block size
 +  * do not use guest CoW filesystem on CoW (ZFS)
 +  * do not use qcow2 files on ZFS
 +  * use 2 zvols per guest FS - one for storage and second one for journal
  
 ===== Tune L2ARC for backups ===== ===== Tune L2ARC for backups =====