FC3 + raw devices

[T. Horsnell]

>T. Horsnell wrote:
>> What's the situation with 'raw' and FC3?
>> I want to get raw access to disks for test
>> purposes but 'man raw' and 'whereis raw'
>> show nothing.
>
>Same as for the rest of Linux: you can access a raw partition as
>/dev/hdXY or /dev/sdXY (depending on technology), where X is a letter
>and Y a number. So the first partition of your first IDE disk is
>/dev/hda1.
>
>To refer to the whole disk, use /dev/hdX or /dev/sdX.
>
>Please note: get this wrong and you could delete your whole system. Be
>careful. Use backups or a separate test system.
>
>Now the real question: what exactly are you trying to do, and why?
>If you just want to see how fast your hard disk goes, try
>hdparm -t /dev/hda
>(or whatever).

Hi James,

Maybe I should have said direct I/O instead of raw. I discovered
the O_DIRECT option to open(2) over the weekend and have been busy
trying to use it.
What I want to do (and what I have been doing on my Alpha system)
is to thrash any new disk I plug in to my SCSI bus, before putting
it to general use. I do this using a long test (at least 48 hours)
of write/read/verify, of records full of random data, of random length,
to random positions on the disk. I want to avoid the cache (which doesnt
happen if I use /dev/sd?) hence the 'raw' requirement.

And, joy of joys, I can now even use smartctl to monitor the disk
health in the process. Its interesting to see the temperature
rise as the disk starts to work hard...

I hadnt heard of hdparm - what a useful tool. It shows buffered
read rates on my 140GB 10Krpm SCSI drives of 75MByte/sec, but on my new
300GB 10Krpm one, I only get 65MBytes/sec. They're all Seagate - and
all < 3 months old. Strange that.


>
>If you want to use raw copying, use dd (and be careful).
>
>Have I mentioned that you need to be careful?

Yes, I'm a bit concerned about this as well. I need to build in
some checks that I'm not doing this on a mounted filesystem.
And maybe a pile of reads, just to flash the 'activity' light on
the chosen drive, would help me avoid finger-troubles.

Cheers,
Terry.

>
>James.
>-- 
>E-mail address: james | Whenever [Richard I] returned to England he always
>@westexe.demon.co.uk  | set out again immediately for the Mediterranean and
>                      | was therefore known as Richard Gare de Lyon.
>                      |     -- '1066 and All That'
>
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