RE: Linux dealing with IBM i blocksizes

The trick is indeed to use sg_dd and force it to use SCSI READ() commands on the SCSI device entry instead of block reads on the block device. It requires an additional parameter (blk_sgio) to use SCSI READ commands instead of read() syscalls.

I do have a kernel patch that allows sector sizes that aren't multiples of 512 (it's relatively trivial to do so), however, it should not be considered something you should do to a production system because I haven't really tested it very well.

-----Original Message-----
From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of DrFranken
Sent: dinsdag 10 maart 2020 13:48
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: Linux dealing with IBM i blocksizes

Aha! Yes I believe I remember this. It's been a while since I messed with this machine.

Thank yoU!


- Larry "DrFranken" Bolhuis

www.Frankeni.com
www.iDevCloud.com - Personal Development IBM i timeshare service.
www.iInTheCloud.com - Commercial IBM i Cloud Hosting.

On 3/9/2020 6:13 PM, Jim wrote:

To read/write those drives on Linux, you may need to use the program
'sg_dd'. It is not installed by default on some Linux distributions.
It's different from regular 'dd', it works by sending SCSI commands
directly instead of going through Linux's block layer.

'sg_dd' is part of a collection of utilities sometimes referred to as
'sgtools'.

Jim


On Mon, Mar 9, 2020 at 6:17 PM Patrik Schindler <poc@xxxxxxxxxx> wrote:

Hello Larry,

Am 09.03.2020 um 23:05 schrieb DrFranken <midrange@xxxxxxxxxxxx>:

Who knows what linux I booted on that thing but it didn't care and
some

of the drives I used were 6607s (I used to have a ton of 'em!)

I'm not 100% but 95% sure that even RedHat didn't "enhance" the block
layer of their "special" kernel to support 520/522 Bytes per sector.

Perhaps a driver bit?

modinfo -p sd_mod yields nothing, so: No.

I used dual port SCSI cards (non-raid) from Adaptec.
68 pin style type with any needed adapters depending on the drives I
was

connecting.

Doesn't make a difference. HBAs, and their drivers are just a way to
enable SCSI devices being used at all, aka, hardware specific driver.
Cable adapters work even a layer below that. :-)

I'm swampped getting ready for 'silly season' (the season in which
we

speak a lot!) so I might not get the thing out and running for a while.

This is a pity. I really want to know about this.

Silly season will be over somewhen, I guess?

:wq! PoC

PGP-Key: DDD3 4ABF 6413 38DE - https://www.pocnet.net/poc-key.asc

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