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Reduce default indirect block size from 128K to 32K.
It dramatically reduces write inflation and metadata (de)compression time
in case of random writes.  It may reduce delete/UNMAP performance due
to more head seeks to read the smaller fragmented indirect blocks,
but that operation is prefetchable, so it should not be too bad.

This value originally was set to 16K, but increased to 128K exactly to
improve delete/UNMAP performance.  But that was done before compressed
ARC support, which introduced new factors.

Ticket: #32736
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amotin committed Apr 30, 2019
1 parent f51399e commit 9987e2b
Showing 1 changed file with 3 additions and 0 deletions.
3 changes: 3 additions & 0 deletions src/freenas/etc/sysctl.conf
Expand Up @@ -16,3 +16,6 @@ net.link.lagg.lacp.default_strict_mode=0

# Force minimal 4KB ashift for new top level ZFS VDEVs.
vfs.zfs.min_auto_ashift=12

# Reduce default indirect block size from 128KB to 32KB.
vfs.zfs.default_ibs=15

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