industrial computer flash performance issues

I have a Nagasaki IPC industrial computer that has an 8 GB
flash drive 
on a 44 pin ATA connector. I have booted FreeBSD 6.2 and 7.0
via a USB 
CD drive and I am getting very bad read performance.

dd if=/dev/ad0 of=/dev/null bs=128k count=100 is only
showing about 
4MB/s. I have also tried a CF via a PCMCIA adapter and I am
also seeing 
about the same performance.

The same CF device connected with a USB adapter (/dev/da0)
gets about 
16MB/s so it seems like some type of ATA driver issue.

>From dmesg:

atapci0: <VIA 8237 UDMA133 controller> port ….
….
ad0: 7765MB <JMAU FDM 8GB 2.0> at ata0-master PIO4

atacontrol cap ad0 shows that dma and overlap is not
supported and all 
the features are no.

Does anyone have any suggestions for improving performance?

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WKK wrote:
> I have a Nagasaki IPC industrial computer that has an 8
GB flash drive
> on a 44 pin ATA connector. I have booted FreeBSD 6.2
and 7.0 via a USB
> CD drive and I am getting very bad read performance.

No wonder, your flash is incapable of DMA mode, at least on
FreeBSD it
seems. You are using PIO mode to transfer data. This
degrades a modern
pc to something like pre-pentium age. So unless you are able
to get it
working in DMA mode (UDMA33 will be fine, the slowest
setting) you won't
see any good performance and interrupt cpu usage will be
extremely high.
It will degrade your whole system.

> The same CF device connected with a USB adapter
(/dev/da0) gets about
> 16MB/s

In that case it is using DMA and not PIO. Maybe the USB
adapter takes
care of that?

To have good flash performance you need an SSD with advanced
controller
chip. One example is Mtron Mobi/PRO Serial ATA SSD, which is
pricey.
Samsung and Transcend have new offerings too, but may offer
less
performance. SLC flash is better than MLC flash, but more
expensive.

And i suspect your flash device without controller chip to
lack support
of wear leveling technique, causing your flash to be weared
out in just
a couple of months of operation with a lot of writes in
/var/log. You
may enable soft updates with long update setting to delay
this wearing
effect.

Regards,

Veronica
fluffles.net
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