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Re: The ultimate TOE design

To: Valdis.Kletnieks@xxxxxx
Subject: Re: The ultimate TOE design
From: David Lang <david.lang@xxxxxxxxxxxxxxxxxx>
Date: Fri, 17 Sep 2004 13:36:14 -0700 (PDT)
Cc: Eric Mudama <edmudama@xxxxxxxxx>, David Stevens <dlstevens@xxxxxxxxxx>, Netdev <netdev@xxxxxxxxxxx>, leonid.grossman@xxxxxxxx, Linux Kernel <linux-kernel@xxxxxxxxxxxxxxx>
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actually the sector based access that is made to modern drives is a very primitive filesystem. if you go back to the days of the MFM and RLL drives you had the computer sending the raw bitstreams to the drives, but with SCSI and IDE this stopped and you instead a higher level logical block to the drive and it deals with the details of getting it to and from the platter.

David Lang

On Fri, 17 Sep 2004 Valdis.Kletnieks@xxxxxx wrote:

Date: Fri, 17 Sep 2004 16:27:31 -0400
From: Valdis.Kletnieks@xxxxxx
To: Eric Mudama <edmudama@xxxxxxxxx>
Cc: David Stevens <dlstevens@xxxxxxxxxx>, Netdev <netdev@xxxxxxxxxxx>,
    leonid.grossman@xxxxxxxx, Linux Kernel <linux-kernel@xxxxxxxxxxxxxxx>
Subject: Re: The ultimate TOE design
On Fri, 17 Sep 2004 00:46:59 MDT, Eric Mudama said:
On Wed, 15 Sep 2004 14:11:04 -0600, David Stevens <dlstevens@xxxxxxxxxx> wrot
e:
Why don't we off-load filesystems to disks instead?

Disks have had file systems on them since close to the beginning...

No, he means "offload the processing of the filesystem to the disk itself".

IBM's MVS  systems basically did that - it used the disk's "Search Key" I/O
opcodes to basically get the equivalent of doing namei() out on the disk itself
(it did this for system catalog and PDS directory searches from the beginning,
and added 'indexed VTOC' support in the mid-80s).  So you'd send out a CCW
(channel command word) stream that basically said "Find me the dataset
USER3.ACCTING.TESTJOBS", and when the I/O completed, you'd have the DSCB (the
moral equiv of an inode) ready to go.



--
There are two ways of constructing a software design. One way is to make it so 
simple that there are obviously no deficiencies. And the other way is to make 
it so complicated that there are no obvious deficiencies.
 -- C.A.R. Hoare

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