Mailinglist Archive: opensuse (2912 mails)

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Re: [SLE] Why Is There a USB Partitions per Device Limit? (and other USB access questions)
  • From: Felix Miata <mrmazda@xxxxxx>
  • Date: Sun, 06 Feb 2005 22:25:55 -0500
  • Message-id: <4206DFC3.3759@xxxxxx>
John Andersen wrote Sun, 6 Feb 2005 16:30:31 -0900:

> On Saturday 05 February 2005 02:51 pm, Felix Miata wrote:

> > Why didn't I get a popup window for every partition on the device (33
> > gross total, minus sdb4)? I know that ATA HD have a generous 63
> > partition limit, while SCSI is limited to 15. Why the lower limit for
> > SCSI, and why is USB treated as though SCSI?

> Sorry for the clipping, but there is a limit of 2 questions per posting. ;-)

I could have written far more. The post followed my worst attempt at a
SuSE install ever. If I wasn't so tired I would have, and eventually,
when I can find the time, and remember it all, I need to. I confined the
post to only one of several installation failure subjects.

> Just because you CAN put that many partitions on a disk does not
> make it wise.

Sometimes just a few isn't possible. When you have upwards of 3
operating systems installed per machine, and rightly keep data
segregated from OS, and from apps also as well where feasible, they can
quickly multiply.

> And when you move it from an environment where
> it could expect to find up to 63 partitions to one where there is
> a limit you suddenly realize why it is NOT wise.

Just a few mega partitions per device have their limitations too. I
choose to keep things in more manageable smaller chunks that really have
no need to grow as disk capacities continue to escalate.

> As to all the WHYs, thats just the way it is. That is how
> the drivers were written, how the products were developed and
> evolved over time.

Sad that complicated and difficult as SCSI is that it had to be further
complicated by co-exising USB treated as SCSI.

> SCSI is probably using only a few bits
> to indicate the partition number, and you exceeded it. You
> can get the source code for any of the drivers involved and
> attempt to re-write it I suppose, but it might be quicker to

Driver writing is for programmers, not users. Nice as it would be if it
did, open source doesn't automatically turn users like me into
competent programmers.

> use directories for those things you are trying to use partitions
> for, and get down to a reasonable number of partitions.

The number available on any particular boot is perfectly reasonable
right now. Windoze or DOS get 2. OS/2 gets at least 3, keeping apps and
OS separate from data, for which only one is not always reasonable.
Linux gets one for /boot, one for /, one for swap, and one for /home
minimum. So, there's about about 9 for a 3 OS system. Double that (minus
1 for swap) for one clone backup for each partition minimum, and the
count is already well past the limit of 15, and leaves nothing for extra
backups for test installs.

> Most hotplug devices end up getting handled by SCIS in
> Linux.

No manual entry for SCSI.
No manual entry for SCIS.
Man entry for hotplug is only one page. It points to
/usr/share/doc/packages/hotplug/README, which has a section on "storage
devices" that says only "To be written by adrian".

> As for your last question:

> >What doc should I be looking for that does or should explain these
> >things?

> You seem to want to know the reasons why Linux was developed
> in a certain way over the many years of its life. There may
> be such a book, bur I doubt it will help you get access to
> all your partitions.

I'm looking for some dialog as much as anything. With other distros I've
used, those with open development like Fedora and Mandrake, there are
forums for dialog with developers that I've yet to find with SuSE.

As long as I'm not handicapped by treating an ATA HD as a SCSI device,
I've no problem. As it is, pretending a USB device is a SCSI device
complicates system management when the system actually has SCSI devices,
which virtually all mine have. NAICT from bugzilla on Fedora and
Mandrake, this pretending USB is SCSI is giving both developers extra
headaches as well as giving users like me extra headaches. From what
I've seen, SCSI that used to work with older distro versions and kernels
commonly breaks in testing of newer releases, and tends to not get fixed
before official release of the new version, leading to threads here like
the current "[SLE] 9.2 scsi install: no fstab found" begun Sat, 5 Feb
2005 01:05:52 -0800.

The 15 partition SCSI limit was designed long long long ago when disks
were relatively infinitesimal compared to what we have now. Even though
the smallest new disks provide huge capacity, the availability of such
capacity in many configurations is simply gross overkill, far more than
someone whose system purpose is something other than collecting as much
stuff as possible.

That leads to finding other uses for all that excess capacity, hence
archival partition backups to so-called "convenient" USB.

Backing up the huge volume of data on 60G, 80G, 120G, 160G & larger
drives is no small challenge. It would be nice to see this unneeded
impediment removed.

> It would seem more profitable in the short run to put the drive
> back where it came from and re-structure the data into fewer partitions
> rather than starting with the history of Linux.

The device is a backup device. It's purpose is for backing up
partitions, and as such, the method most easily serving the purpose is
exact sector by sector cloning. A major idea behind USB is
simplification, both of physical, and of logical connection, including
device sharing. So, this device has partitions from multiple systems,
each with multiple partitions. The artificial limitation built into SCSI
is an insurmountable obstacle here, forcing me to return to opening
cases, shutting down systems, plugging in internally, rebooting, etc,
etc, etc.

> Look into Kwickdisk or Kdiskfree. Nice GUI mounting tools. Also read
> the manuals that came with your Boxed set.

I hope it turns out to be a lot better than the online docs I've found
so far. Used to be online docs were sufficient. It took an hour
yesterday to initialize the KDE help system, and it turned up nothing of
much use for USB when it finally finished.
"He who believes in me will live, even though he dies; and
whoever lives and believes in me will never die." John 11:25 NIV

Team OS/2 ** Reg. Linux User #211409

Felix Miata ***

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