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From: Ollivier Robert <roberto@keltia.freenix.fr>
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Subject: Re: "High" cpu usage when using ZFS cache device
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According to Christer Solskogen:
> See, that is why I think it is a ZFS issue. Because I did that.
> I created a UFS filesystem on the same usb stick. Mounted it and did a
> "dd if=/dev/zero of=/mnt/file".
> The systemload goes +0.6 instead if +10.3.

Do not forget that everything that is read/written from/to USB devices goes through the CPU (no DMA or anything for USB devices).

-- 
Ollivier ROBERT -=- FreeBSD: The Power to Serve! -=- roberto@keltia.net
In memoriam to Ondine, our 2nd child: http://ondine.keltia.net/