Subject: Re: Extremely slow IO response times + panic on 3.0_BETA
To: None <>
From: Michael van Elst <>
List: port-i386
Date: 07/14/2005 05:50:18 (Dan LaBell) writes:

>but I decided to test it out on my pc first.   It seemed completely 
>zeroed (fresh) , but
>to verify that ,and to do a read-test, I did  a: dd if=/dev/rwd1d 
>bs=128k | sum
>Afterwards, there would be about a 3 second window, where I could type, 
>maybe switch vt's,
>but, then a long hang, which seemed last around a minute, possibly 
>longer, before any kind of responsiveness was returned.  I'm wondering 
>if the affect could be tuned away?

This must be unrelated, since you are reading from a raw device. No
filecache activity is involved.

I guess you fall over the end of rwd1d. The size of the raw device
does not reflect the size of the disk, so it is possible to read
beyond the end and generate I/O errors that are then naively retried.

During the retries you will experience that the system is almost

                                Michael van Elst
                                "A potential Snark may lurk in every tree."