[OpenIndiana-discuss] RAIDZ performance

[Timothy Coalson]

A shot in the dark here, but what controller is it using?  If it is using a
PCIe 1.0 x1 interface, that could explain the slowdown, and the much faster
reads.

Tim

On Wed, Feb 20, 2013 at 1:05 PM, Reginald Beardsley <pulaskite at yahoo.com>wrote:

> On an N40L running oi_151a7 w/ four ST2000DM001 drives I'm seeing a large
> drop in performance for RAIDZ2 vs RAIDZ1 which surprises me.
>
> The discussions google found were not entirely enlightening and not OI
> based.  How much CPU does a small OI based ZFS server need?
>
> For 3 disk RAIDZ1 I get 189-199 MB/s and 179 MB/s for 4 disk RAIDZ1.  But
> for 4 disk RAIDZ2 I get 109-118 MB/s.  I expected some loss in performance,
> but not that much.  These are measured writing 64 GB of /dev/zero to the
> RAIDZ filesystem from a console window.
>
> For a 256 GB file I got 111 MB/s writing and 279 MB/s reading 4 disk
> RAIDZ2.
>
> System is unloaded w/ 4 GB of ECC DRAM using a 4-way mirror rpool in the
> s0 slices w/ RAIDZ in the s1 slices.
>
> Does the drop in RAIDZ2 write performance correspond to other people's
> experience? If so, why such a large hit?  top suggests the system has spare
> CPU capacity (30-50% idle). For my current needs things look good, but I'd
> like to understand why a bit better.  Or if there is some tuning I should
> do.
>
> Have Fun!
> Reg
>
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