Thanks Bobby
That seems to make sense now
i.e. "The I/O to tape has a
buffer. The data does not go directly to the
tape"
Saying this, then should be no gaps as presumed before as
illustrated below ?
- - - - - - - - - - - -
- - - - - - -
S1 15mb
###############################
- - - - - - - - - - - -
- - -- - - - - - - - - - - - - - - - - - -
-
S2 15mb
########################
- - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - -
S3 15mb
########################
- - - - - - - - - - - - - -
-- - - - - - - - - - - - - - - - - - -
-
S4 10mb
####
#### ####
####
- - - - - - - - - - - -- - - - - -
- - - - - - - - - - - - - - - - -
Regards
Dave
-----Original Message-----
From: Bobby Williams
[mailto:bobbyrjw AT comcast DOT net]
Sent: 06 September 2007 13:25
To: 'Kevin
Whittaker'; Clooney, David; 'Justin Piszcz'
Cc:
veritas-bu AT mailman.eng.auburn DOT edu
Subject: RE: [Veritas-bu] MPX
Explanation
When the buffer is full, then buffer empties to the
tape.
It works the same no matter how many MPX streams you have
(even 1 stream).
The I/O to tape has a buffer. The data does not go
directly to the tape.
The OS or the application can set the number and size of
the buffers.
When a buffer is full, it goes to tape. The last
buffer is emptied when the
I/O driver closes the process.
Bobby Williams
2205 Peterson
Drive
Chattanooga,
Tennessee 37421
423-296-8200
-----Original Message-----
From:
veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On
Behalf Of Kevin
Whittaker
Sent: Thursday, September 06, 2007 8:00
AM
To: Clooney, David; Justin
Piszcz
Cc:
veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] MPX
Explanation
Should have been more clear. I mean till the buffer
is full and it is ready
to write it to the tape.
-----Original Message-----
From: Clooney, David
[mailto:david.clooney AT bankofamerica DOT com]
Sent: Thursday, September 06, 2007 7:59
AM
To: Kevin Whittaker; Justin
Piszcz
Cc:
veritas-bu AT mailman.eng.auburn DOT edu
Subject: RE: [Veritas-bu] MPX
Explanation
Thanks Kev
Ready for what exactly ?
Dave
-----Original Message-----
From: Kevin Whittaker
[mailto:Kevin.Whittaker AT syniverse DOT com]
Sent: 06 September 2007
12:57
To: Justin Piszcz; Clooney,
David
Cc:
veritas-bu AT mailman.eng.auburn DOT edu
Subject: RE: [Veritas-bu] MPX
Explanation
I would agree, that is what I have seen happen. If
one stream lags behind
it just skips putting it on the drive until it is ready.
-----Original Message-----
From:
veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On
Behalf Of Justin
Piszcz
Sent: Thursday, September 06, 2007 7:19
AM
To: Clooney, David
Cc:
veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] MPX
Explanation
On Thu, 6 Sep 2007, Clooney, David
wrote:
> Hi All
>
>
>
> Is there any chance someone could clarify MPX for
me.
>
>
>
> If you have MPX set to 4 for example and there are 4
streams hitting
> the drive. All 4 streams are writing in parallel as
the tape spins.
> And if 3 streams are writing at 15mb/sec and 1
stream is writing at
> 10mb/sec, would the slower of the streams be a
bottle neck for the
> other 3. My lack of the tape technology is most
probably to blame, I
> am thinking of each stream the way fragments work on
a tape , finish 1
> start the next , please tell me this is not the same
on each stream.
>
That is a good question, but I don't think so(?) I think
the 3 streams a
15MB/s continue to truck along and the 10MB/s stream
writes at 10MB/s but
its more stretched out,
example:
15MB/s stream:
# # # # # # # # # # # # # # #
#
10MB/s stream:
# # # #
# # # #
#
Justin.
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