On 2018-04-24 01:30, Grant Taylor <gtaylor(a)tnetconsulting.net> wrote:
> On 04/23/2018 04:15 PM, Warner Losh wrote:
>> It's weird. These days lower LBAs perform better on spinning drives.
>> We're seeing about 1.5x better performance on the first 30% of a drive
>> than on the last 30%, at least for read speeds for video streaming....
> I think manufacturers have switched things around on us. I'm used to
> higher LBA numbers being on the outside of the disk. But I've seen
> anecdotal indicators that the opposite is now true.
That must have been somewhere in the middle of history in that case. Old
(proper) drives had/have track 0 at the outer edge. The disk loaded the
heads after spin up, and that was at the outer edge, and then you just
locked on to track 0, which should be near.
Heads had to be retracted for the disk pack to be replaced.
But this whole optimization for swap based on transfer speeds makes no
sense to me. The dominating factor in spinning rust is seek times, and
not transfer speed. If you place the swap at one end of the disk, it
won't matter much that transfers will be faster, as seek times will on
average be much longer, and that will eat up any transfer gain ten times
over before even thinking. (Unless all your disk ever does is swapping,
at which time the heads can stay around the swapping area all the time.)
Which is also why the file system for RSX (ODS-1) placed the index file
(equivalent of the inode table) at the middle of the disk by default.
Not sure if Unix did that optimization, but I would hope so. (Never dug
into that part of the code.)
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt(a)softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
Computer pioneer Niklaus Wirth was born on this day in 1934; he basically
designed ALGOL, one of the most influential languages ever, with just
about every programming language in use today tracing its roots to it.
His name is pronounced "vurt" but he would accept "worth", and he joked
that you could call him by name or by value (you need to know ALGOL to
understand).
--
Dave Horsfall DTM (VK2KFU) "Those who don't understand security will suffer."
>Date: Mon, 23 Apr 2018 13:51:07 -0400
>From: Clem Cole <clemc(a)ccc.com>
>To: Ron Natalie <ron(a)ronnatalie.com>
>Cc: Tim Bradshaw <tfb(a)tfeb.org>, TUHS main list <tuhs(a)minnie.tuhs.org>
>Subject: Re: [TUHS] /dev/drum
>Message-ID:
> <CAC20D2PEzAayjfaQN+->kQS=H7npcEZ_OKXL1ffPxak5b2ENv4Q(a)mail.gmail.com>
>Content-Type: text/plain; charset="utf-8"
... some stuff removed ...
>​Exactly... For instance an RK04 was less that 5K blocks (4620 or some
>such - I've forgotten the actually amount). The disk was mkfs'ed to the
>first 4K and the left over was give to the swap system. By the time of
>4.X, the RP06 was 'partitioned' into 'rings' (some overlapping). The 'a'.
>partition was root, the 'b' was swap and one fo the others was the rest.
>Later the 'c' was a short form for copying the entire disk.
Wondered why, but I guess now I know that's the reason Digital UNIX on
alpha used the same disk layout. From a AlphaServer DS10 running
DU4.0g, output "disklabel -r rz16a"
# /dev/rrz16a:
type: SCSI
disk: BB009222
label:
flags:
bytes/sector: 512
sectors/track: 168
tracks/cylinder: 20
sectors/cylinder: 3360
cylinders: 5273
sectors/unit: 17773524
rpm: 7200
interleave: 1
trackskew: 66
cylinderskew: 83
headswitch: 0 # milliseconds
track-to-track seek: 0 # milliseconds
drivedata: 0
8 partitions:
# size offset fstype [fsize bsize cpg] #
NOTE: values not exact
a: 524288 0 AdvFS # (Cyl. 0 - 156*)
b: 1572864 524288 swap # (Cyl. 156*- 624*)
c: 17773524 0 unused 0 0 # (Cyl. 0 - 5289*)
d: 0 0 unused 0 0 # (Cyl. 0 - -1)
e: 0 0 unused 0 0 # (Cyl. 0 - -1)
f: 0 0 unused 0 0 # (Cyl. 0 - -1)
g: 4194304 2097152 AdvFS # (Cyl. 624*- 1872*)
h: 11482068 6291456 AdvFS # (Cyl. 1872*- 5289*)
> From: "Ron Natalie"
> I'm pretty sure that swapping in V6 took place to a major/minor number
> configured at kernel build time.
Yup, in c.c, along with the block/character device switches (which converted
major device numbers to routines).
> You could create a dev node for the swap device, but it wasn't used for
> the actual swapping.
Yes.
> We actually dedicated a full 1024 block RF11 fixed head to the system in
> the early days
Speaking of fixed-head disks, one of the Bell systems used (IIRC) an RS04
fixed-head disk for the root. DEC apparently only used that disk for swapping
in their OS's... So the DEC diagnsotics felt free to scribble on the disk.
So, Field Circus comes in to work on the machine... Ooops!
Noel
> From: Clem Cole
> To be honest, I really don't remember - but I know we used letters for
> the different partitions on the 11/70 before BSD showed up.
In V6 (and probably before that, too), it was numbers:
http://minnie.tuhs.org/cgi-bin/utree.pl?file=V6/usr/man/man4/rp.4
So on my machine which had 2 x 50MB CalChomps, with a Diva controller, which
we had to split up into two partition each (below), they were dv00, dv01, dv10
and dv11. Letters for the partitions made it easier...
> The reason for the partition originally was (and it must have been 6th
> edition when I first saw it), DEC finally made a disk large enough that
> number of blocks overflowed a 16 bit integer. So splitting the disk
> into smaller partitions allowed the original seek(2) to work without
> overflow.
No, in V6 filesystems, block numbers (in inodes, etc - also the file system
size in the superblock) were only 16 bits, so a 50MB disk (100K blocks) had to
be split up into partitions to use it all. True of the RP03/04 in V6 too (see
the man page above).
Noel
Ingo wrote:
> i have been working hard to reduce the number of options of low usefulness
Ah, soothing classical Unix Musik, so rare in the cacophonous Linux era.
Doug
Ray Tomlinson, computer pioneer, was born on this day in 1941. He is
credited with inventing this weird thing called "email" on the ARPAnet, in
particular the "@" sign to designate a remote host (although some jerk --
his name is not important -- is claiming that he was first).
--
Dave Horsfall DTM (VK2KFU) "Those who don't understand security will suffer."
Clem Cole:
On the other hand, we still 'dump core' and use the core files for
debugging. So, while the term 'drum' lost its meaning, 'core file' - might
be considered 'quaint' by todays hacker, it still has meaning.
====
Just as we still speak of dialling and hanging up the phone,
electing Presidents, and other actions long since made obsolete
by changes of technology and culture.
Norman Wilson
Toronto ON
> From: Warner Losh
> Drum memory stopped being a new thing in the early 70's.
Mid 60's. Fixed-head disks replaced them - same basic concept, same amount of
bits, less physical volume. Those lasted until the late 70's - early PDP-11
Unixes have drivers for the RF11 and RS0x fixed-head disks.
The 'fire-hose' drum on the GE 645 Multics was the last one I've heard
of. Amusing story about it here:
http://www.multicians.org/low-bottle-pressure.html
Although reading it, it may not have been (physically) a drum.
> There never was a drum device, at least a commercial, non-lab
> experiment, for the VAXen. They all swapped to spinning disks by then.
s/spinning/non-fixed-head/.
Noel
Does anyone know if UToronto's MRS database system (from about 1979) has
survived? It was described in:
Robert Hudyma, John Kornatowski, Ivor Ladd. MRS: A microcomputer
database management system. Proceedings of the 1981 ACM SIGSMALL
symposium on Small systems and SIGMOD workshop on Small database
systems, pp 174-180.
Apparently it was distributed to over 50 unix sites. This is the
software which became the MISTRESS and later EMPRESS products.
De
