Thank you for the morning read. Very informative. That helps. So repacking files and splitting or adding disc will help.
Get Outlook for iOS<https://aka.ms/o0ukef>
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From: HP-3000 Systems Discussion <[log in to unmask]> on behalf of HP3000-L automatic digest system <[log in to unmask]>
Sent: Friday, March 5, 2021 11:00:01 PM
To: [log in to unmask] <[log in to unmask]>
Subject: HP3000-L Digest - 4 Mar 2021 to 5 Mar 2021 (#2021-26)
This Message Is From an External Sender This message came from outside of Veritiv.
There are 2 messages totaling 196 lines in this issue.
Topics of the day:
1. [EXT]: LDEV limits? (2)
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----------------------------------------------------------------------
Date: Thu, 4 Mar 2021 23:27:31 -0800
From: Stan Sieler <[log in to unmask]>
Subject: Re: [EXT]: LDEV limits?
Re: limit on number of files on an "LDEV".
It's not a simple answer, partially because of how files are tracked by
MPE/iX.
A disk file is composed of zero or more areas of disk, called "extents".
(On Classic MPE, a file was
composed of one to 30 extents ... MPE/iX has larger limits.)
Every mounted disk ("LDEV" for now) is part of some volume set (e.g., LDEV
1 is always part MPEXL_SYSTEM_VOLUME_SET,
which I call $SYS for short).
(A "volume set" is a named collection of one or more LDEVs (essentially,
but that's close enough).)
Every disk in a volume set has a Label Table on it ... this is a permanent
data structure that keeps
track of file-oriented things. If you create a new file, A.B.C, an entry
is made in an appropriate Label Table
(of which, perhaps more later). Entries in a Label Table are $300 bytes
long (768 bytes).
The label allocated when you created A.B.C is enough to track 20 to 60
extents (I forgot which, but
I suspect it's 60).
If you expand the file, adding more extents (as typically happens with log
files), when the initial 60
extent slots are used up, another block of 60 extent slots are allocated
from the *same* Label Table
that the file label is on (even if the volume set has more than one disk).
One or two obscure other items can also use entries in the Label Table, but
I'll ignore them.
So ... since the Label Table itself is an object on disk (and, for that
matter, a not easily expandable
object), it has a maximum number of entries in it ... generally about
262,144 ($40000) (perhaps minus one,
and minus a small handful of reserved slots at the start).
That quarter-of-a-million free entries are used for file labels, extent
blocks, and the obscure items.
That means:
1. you could have about 1/4 million file labels in a Label Table ... if
none of them
had more than 60 extents.
2. you could have about 25,000 file labels in a Label Table, if each
file had about 600 extents
...you get the idea: there is no one magic number of file labels I can
state is a true maximum.
(Oh, it approaches a quarter million, but that's with *small* files :)
(The "more later"...yeah, why not...)
If a volume set has, say, two disks in it (e.g., $SYS has LDEVs 1 and 2),
then when you create
file B.FOO.SALES (and FOO.SALES is "homed" to $SYS), then usually either
LDEV 1 or LDEV 2
is picked as the Label Table to create the file label in (you can control
that via a "DEV=" specification,
otherwise it's an obscure automagic algorithm that chooses between the
available LDEVs in a volume set).
That means that, roughly, a two disk volume set could potentially have up
to about 1/2 million files ...
if they were all smallish files.
Note that this is *completely* different from (or, for the Brits, "to") the
limits on the number of
files in a group (or in any directory, for that matter).
...that's a much smaller limit, and Donna pointed out some of Allegro's
free tools to inspect/handle
such limits/problems.
Stan Sieler
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------------------------------
Date: Fri, 5 Mar 2021 13:29:50 +0000
From: Craig Lalley <[log in to unmask]>
Subject: Re: [EXT]: LDEV limits?
Great post, thanks Stan for the early morning reading.
-Craig
On Thursday, March 4, 2021, 11:27:49 PM PST, Stan Sieler <[log in to unmask]> wrote:
Re: limit on number of files on an "LDEV".
It's not a simple answer, partially because of how files are tracked by
MPE/iX.
A disk file is composed of zero or more areas of disk, called "extents".
(On Classic MPE, a file was
composed of one to 30 extents ... MPE/iX has larger limits.)
Every mounted disk ("LDEV" for now) is part of some volume set (e.g., LDEV
1 is always part MPEXL_SYSTEM_VOLUME_SET,
which I call $SYS for short).
(A "volume set" is a named collection of one or more LDEVs (essentially,
but that's close enough).)
Every disk in a volume set has a Label Table on it ... this is a permanent
data structure that keeps
track of file-oriented things. If you create a new file, A.B.C, an entry
is made in an appropriate Label Table
(of which, perhaps more later). Entries in a Label Table are $300 bytes
long (768 bytes).
The label allocated when you created A.B.C is enough to track 20 to 60
extents (I forgot which, but
I suspect it's 60).
If you expand the file, adding more extents (as typically happens with log
files), when the initial 60
extent slots are used up, another block of 60 extent slots are allocated
from the *same* Label Table
that the file label is on (even if the volume set has more than one disk).
One or two obscure other items can also use entries in the Label Table, but
I'll ignore them.
So ... since the Label Table itself is an object on disk (and, for that
matter, a not easily expandable
object), it has a maximum number of entries in it ... generally about
262,144 ($40000) (perhaps minus one,
and minus a small handful of reserved slots at the start).
That quarter-of-a-million free entries are used for file labels, extent
blocks, and the obscure items.
That means:
1. you could have about 1/4 million file labels in a Label Table ... if
none of them
had more than 60 extents.
2. you could have about 25,000 file labels in a Label Table, if each
file had about 600 extents
...you get the idea: there is no one magic number of file labels I can
state is a true maximum.
(Oh, it approaches a quarter million, but that's with *small* files :)
(The "more later"...yeah, why not...)
If a volume set has, say, two disks in it (e.g., $SYS has LDEVs 1 and 2),
then when you create
file B.FOO.SALES (and FOO.SALES is "homed" to $SYS), then usually either
LDEV 1 or LDEV 2
is picked as the Label Table to create the file label in (you can control
that via a "DEV=" specification,
otherwise it's an obscure automagic algorithm that chooses between the
available LDEVs in a volume set).
That means that, roughly, a two disk volume set could potentially have up
to about 1/2 million files ...
if they were all smallish files.
Note that this is *completely* different from (or, for the Brits, "to") the
limits on the number of
files in a group (or in any directory, for that matter).
...that's a much smaller limit, and Donna pointed out some of Allegro's
free tools to inspect/handle
such limits/problems.
Stan Sieler
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