Re: File Systems vs. Raw Devices

In article <1994May25.183843.15365_at_rossinc.com>

           joelga_at_rossinc.com "Joel Gary" writes:

> In article <2rnj3g$npt_at_samba.oit.unc.edu> Harold.Bauer_at_launchpad.unc.edu
> (harold bauer) writes:
> >
> > Experiences using file systems and raw devices.
> > What are the administrative and operational problems of the two?
>
> Inevitably, someone will create a unix filesystem over your raw system.

Raw devices are a complete bitch to recover as well. 'dd' rules the roost here. If you're planning on shunting databases from machine to machine they're not a wise idea.

However!

Raw devices squeeze more space out of your disks. ( No 10% or thereabouts overhead for superblock information ).

> > What are the performance gains (is there really a 50% gain in using
> > raw devices over file systems)?
>
> No, more like 10-15%, at least on BSD SunOS systems.

Yeah, in my experience ( 6G databases ), 10-15% is a pretty fair estimate.

One thing to note, however. VERY IMPORTANT!!!!

If you're planning to use raw devices on a disk, partition a must be 1 block in size only. ORACLE needs this. I learned this from bitter experience.....

> --
> Joel Garry joelga_at_amber.rossix.com Compuserve 70661,1534
> These are my opinions, not necessarily those of Ross Systems, Inc.
> %DCL-W-SOFTONEDGEDONTPUSH, Software On Edge - Don't Push.
 

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