Re: Weak disk I/O performance on daX compared to adaX, was: Re: dd performance [was Re: Call for Foundation-supported Project Ideas]
Date: Tue, 14 Dec 2021 05:57:12 UTC
On Tue, Dec 14, 2021 at 04:06:50AM +0100, Stefan Blachmann wrote:
>
> So my questions:
> - Why does FreeBSD use the da driver instead of the ada driver for
> drives on SATA ports 1-4?
A look at the Z240 block diagram in the maintenance and service guide
(document number 669531-005) reveals the presence of two different HBAs. First
there is one raid controller (Intel or LSI depending on the bought options)
and, secondly, a plain AHCI adapter. One can only boot from the first
controller.
It is usual for HP/HPe machines to provide a firmware setting
permitting the disablement of the raid controller. When used, this setting
morphs the controller to a plain AHCI HBA. Doing this on my Proliants did
improve I/O performances up to the satisfying point of the disks themselves
becoming the bottleneck. I recommend using the AHCI mode, especially if you
are storing zpools.
You should also be aware that not all SATA ports are made equal on
this motherboard. In the manual some are marked as 6 Gb/s while other are
3 Gb/s. (SATA 3 vs. SATA 2?) Some ports can also be configured for eSATA
operation, this should be checked.
--
%!PS -- Bertrand Petit
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