inodes, partitions, and Re: Advise about Wren 7 SCSI disk.

[Ed Hew]

In article <1991Jan24.194219.6604 at world.std.com> steveo at world.std.com (Steven W Orr) writes:

>I am about to decide to buy a 1.2G Seagate Wren 7 SCSI drive.

We are very pleased with our 660meg Wren 6 SCSI boot drive.

> The
>question has been raised that I might not be able to take advantage
>of the space on the disk because each physical device has a limited
>number of inodes.

While there are other (solved) problems that might prevent you from
using all the cylinders of very large drives, lack of inodes is not
a major factor.  Lack of inodes within a given filesystem can be a
headache (like in /dev/news), but that's a different problem.

> Could someone explain the relationship between the
>inodes per disk (which I think is called a file system) and the
>inodes per partition? If there is a max can I configure it or is it
>fixed?

All the following "as of the last time I checked".

First note that SCO UNIX 3.2.* can support 2 SCSI host adapters each
of which can support 2 SCSI hard drives.  I'm told that this limitation
only exists due to the SysV maximum of 4 availabie minor device numbers
for individual hard drives.

Each hard drive will support up to 4 partitions.
Each partition will support up to 7 filesystems plus an entry for the
	device (eg, active_UNIX_partition=/dev/hd0a).  The active UNIX
	partition will house the mandatory swap area and the suggested
	'recover' area.  You may also wish to have a scratch filesystem.  
	This gives you 4+7+7+7 filesystems available per drive (the
	first filesystem on the active partition will be root).
Each filesystem will support up to 64K (that's 16*16*16*16=65536)
	less 2 (reserved) inodes per filesystem.

One free inode gives you the ability to "add" one file, assuming you
have some free diskblocks for the "optional" data.  :-)  By default
about 25% of the free space in each filesystem is allocated to the
inode table.

That adds up to a lot of potential inodes if the filesystems are
each able to be physically large enough to get the max # of inodes.
A rough guestimate suggests that you'd hit the optimal SysV inode
max with a 5-ish-Gig drive.

Now it's up to you to determine the optimum layout.  You can use
the -v option to divvy to access "virtual" (non-active) partitions.

I would recommend:	man divvy
			man fdisk
			man mkfs

> Also, does anyone have anything good or bad to say about this
>particular drive? The best price I've found so far is $2800 for the
>bare drive. I'm also interested in speculation about the prices
>dropping substantially in the near future.

History suggests a constant decline in the $/meg storage cost.
I don't see technology holding back a continuation of this trend.
There are of course bumps in the graph.  Buy when you _need_ it.

>Email me, and if there's enough clamor I'll summarize. 

I'll post the answer to this as there are likely others wondering
what the bottom line is.  I'll email you the illustration using
our site as an example.

Again, corrections and elaborations from those more knowledgeable
are always welcome.

>Steven W. Orr      steveo at world.std.com     uunet!world!steveo
--
  Ed. A. Hew  <edhew at xenitec.on.ca>,  XeniTec Consulting Services
  or if you're really stuck:  ..!{watmath|lsuc}!xenitec!eah
  [sco.opendesktop newsgroup <=> mlist gateway maintainer]