raw disk device

raw disk device

Post by Ben Coh » Sat, 25 May 1996 04:00:00



We have a new sparc20 running SUN OS 4.1.4 and are installing Sybase
4.9.1 on it.

I`d like to take device sd0h and use it as a raw character device for
sybase.

I`ve moved everyting off of sd0h and unmounted it and removed it from fstab.

However, in all of our Sun books, I can't find anything about how to
convert this partition to a raw character device ( rsd0h or something
like that ).

This is probably a really simple thing but I just can`t find any thing on it.

Thanks in advance for any help.


 
 
 

raw disk device

Post by Michael Salmo » Sat, 25 May 1996 04:00:00



> We have a new sparc20 running SUN OS 4.1.4 and are installing Sybase
> 4.9.1 on it.

> I`d like to take device sd0h and use it as a raw character device for
> sybase.

> I`ve moved everyting off of sd0h and unmounted it and removed it from fstab.

> However, in all of our Sun books, I can't find anything about how to
> convert this partition to a raw character device ( rsd0h or something
> like that ).

> This is probably a really simple thing but I just can`t find any thing on it.

You don't convert a disk partition to a raw character device, it always is one:

  eos93 ~ 75 > ls -l /dev/{,r}sd0h
crw-r-----   1 root     operator  17,   7 Feb  1 16:08 /dev/rsd0h
brw-r-----   1 root     operator   7,   7 Dec 28  1992 /dev/sd0h

--
? 1995,1996 Michael Salmon
All opinions expressed in this article remain the property of
Michael Salmon.  Permission is hereby granted for use in
followup articles, FAQ's and digests.

 
 
 

raw disk device

Post by Pablo Sanch » Sat, 25 May 1996 04:00:00




> > We have a new sparc20 running SUN OS 4.1.4 and are installing Sybase
> > 4.9.1 on it.

> > I`d like to take device sd0h and use it as a raw character device for
> > sybase.

> > I`ve moved everyting off of sd0h and unmounted it and removed it from fstab.

> > However, in all of our Sun books, I can't find anything about how to
> > convert this partition to a raw character device ( rsd0h or something
> > like that ).

> > This is probably a really simple thing but I just can`t find any thing on it.

> You don't convert a disk partition to a raw character device, it always is one:

>   eos93 ~ 75 > ls -l /dev/{,r}sd0h
> crw-r-----   1 root     operator  17,   7 Feb  1 16:08 /dev/rsd0h
> brw-r-----   1 root     operator   7,   7 Dec 28  1992 /dev/sd0h

It's my understanding (may be wrong?) that Sun ships their disks with
write-caching enabled.  How do folks running Suns disable this when
converting such disks to raw?

Pablo Sanchez              | Ph # (415) 933.3812        Fax # (415) 933.2821

===============================================================================
I am accountable for my actions.   http://reality.sgi.com/pablo [ /Sybase_FAQ ]

 
 
 

raw disk device

Post by Konstantin Ginzbur » Sat, 25 May 1996 04:00:00




>> > We have a new sparc20 running SUN OS 4.1.4 and are installing Sybase
>> > 4.9.1 on it.

>> > I`d like to take device sd0h and use it as a raw character device for
>> > sybase.

>> > I`ve moved everyting off of sd0h and unmounted it and removed it from fstab.

>> > However, in all of our Sun books, I can't find anything about how to
>> > convert this partition to a raw character device ( rsd0h or something
>> > like that ).

>> > This is probably a really simple thing but I just can`t find any thing on it.

>> You don't convert a disk partition to a raw character device, it always is one:

>>   eos93 ~ 75 > ls -l /dev/{,r}sd0h
>> crw-r-----   1 root     operator  17,   7 Feb  1 16:08 /dev/rsd0h
>> brw-r-----   1 root     operator   7,   7 Dec 28  1992 /dev/sd0h

>It's my understanding (may be wrong?) that Sun ships their disks with
>write-caching enabled.  How do folks running Suns disable this when
>converting such disks to raw?

Under SunOS disks are represented in two ways: as block device,
and as character (raw) device.  SunOS file system works with
block devices.  You have to mount corresponding block device at
desired point in directory tree.  That way file system
recognizes the device and uses cache features.  File system
does not recognize raw devices, in fact it doesn't know they
exist.  Therefore, you don't have to disable any features of
file system for raw devices - they don't have any.  You also
don't have to 'convert' devices - all you have to do is specify
raw device name (/dev/rdsk/xxx) instead of block device name
(/dev/dsk/xxx) for a disk or partition (they have both names),
when you assign it to something (like sybase).  Sybase handles
raw space on its own, without Sun's file system knowing this
space exists.
 
 
 

raw disk device

Post by Scott Gr » Thu, 30 May 1996 04:00:00




Quote:>>It's my understanding (may be wrong?) that Sun ships their disks with
>>write-caching enabled.  How do folks running Suns disable this when
>>converting such disks to raw?

>Under SunOS disks are represented in two ways: as block device,
>and as character (raw) device.  SunOS file system works with
>block devices.  You have to mount corresponding block device at
>desired point in directory tree.  That way file system
>recognizes the device and uses cache features.  File system

I think Pablo was refering to the hardware write-back cache on the
drive itself, not the OS block cache.  My guess is that the raw
character driver probably turns off this feature by default (I
would hope)...either that or one would hope that SQL server is
requesting syncronous writes.  I'll see if I can get some details
on this.

-scott
--


   http://www.voicenet.com/~gray/sqsh.html

 
 
 

raw disk device

Post by Bob Gagno » Thu, 30 May 1996 04:00:00




> > We have a new sparc20 running SUN OS 4.1.4 and are installing Sybase
> > 4.9.1 on it.

> > I`d like to take device sd0h and use it as a raw character device for
> > sybase.

> > I`ve moved everyting off of sd0h and unmounted it and removed it from fstab.

> > However, in all of our Sun books, I can't find anything about how to
> > convert this partition to a raw character device ( rsd0h or something
> > like that ).

> > This is probably a really simple thing but I just can`t find any thing on it.

> You don't convert a disk partition to a raw character device, it always is one:

>   eos93 ~ 75 > ls -l /dev/{,r}sd0h
> crw-r-----   1 root     operator  17,   7 Feb  1 16:08 /dev/rsd0h
> brw-r-----   1 root     operator   7,   7 Dec 28  1992 /dev/sd0h

> --
> ? 1995,1996 Michael Salmon
> All opinions expressed in this article remain the property of
> Michael Salmon.  Permission is hereby granted for use in
> followup articles, FAQ's and digests.Check your OS Specific install document provided with your SYBASE

install CD There is data on this raw device allocation process.  Also a
good book you might get is the SYBASE DBA survival guide.  It has
numerous examples of UNIX specific device management as an example it
illustrates diskdump device specification.
 
 
 

1. raw disk device i/o

From previous threads on this topic, it seems to be the conventional wisdom
that raw disk i/o is unbuffered and that unbuffered i/o is synchronous i/o.
Is this documented somewhere?  I've never seen it.  Or is this a convention
that all the various raw disk device drivers have been adhering to so far?

--

--

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