freebsd-questions Digest, Vol 284, Issue 11
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Sun Nov 15 18:21:52 UTC 2009
> Date: Sat, 14 Nov 2009 20:29:59 -0600
> From: CyberLeo Kitsana <cyberleo at cyberleo.net>
> Subject: [FreeBSD Questions] Filesystem image as root
> To: FreeBSD Questions <freebsd-questions at freebsd.org>
> Cc: CyberLeo <cyberleo at cyberleo.net>
> Message-ID: <4AFF67A7.6040109 at cyberleo.net>
> Content-Type: text/plain; charset=ISO-8859-1
> I have been thinking and experimenting for weeks, but I
> cannot figure
> this out.
> I have an Intel SS4200 NAS that I wish to use as a ZFS NAS
> with FreeBSD 8.0.
> The device has 4 SATA bays, and I don't want to use one for
> a UFS root disk.
> I don't want to use up hundreds of megabytes of RAM
> preloading an
> mfsroot that can never shrink.
> The single IDE connector is accessible via the legacy ISA
> ports, and is
> thus limited to PIO modes (about 1.6MB/sec max, even with
> an actual hard
> drive instead of a CF card).
You are off by an order of magnitude (base 2 or 10):
Pio mode 0 is ~3.3 MB/s
Pio mode 4 is ~16.7 MB/s
You can probably set PIO mode 4 for with:
# atacontrol mode ad0 PIO4
I am currently using ~ 159MB on my root partition,
At 16.7MB/s that is a 10 second load time; and as you said, frequently used files will be cached. (I have a CF card that has 15MB/s symmetric read/write. Don't know how special it is.)
With a CF card there should be no seek delay of ~ 10 ms (for reads anyway, deleting blocks probably takes 10ms).
<SNIPPED pivot_root attempt I can't help with.>
My summary: maybe you are trying too hard :)
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