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| Title: | ase |
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| Moderator: | SMURF::GROSSO |
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| Created: | Thu Jul 29 1993 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2114 |
| Total number of notes: | 7347 |
1964.0. "MEMORY CHANNEL programming Q's" by namix.fno.dec.com::jpt (FIS and Chips) Thu Mar 20 1997 11:19
I have very specific (and important) questions from
ISV and Industrial customer, which address some features
of MEMORY CHANNEL. As there is no MC dedicated conference,
I'll start from here:
#1 mmap(), shared memory and MC
Would it be possible to map mmap() file to MC shared memory? If
this would be possible, are there any restrictions we should be
aware of?
#2 mmap(), DRD
Can DRD devices be mmap()'d (or LSM/DRD volume)?
#3 Synch.
If DRD/LSM supports mmap(), would DLM be best way to synch things
between cluster nodes?
#4 File system file mmap()
Any recommendations what would be best way to mmap() file on
file system and synch it between two systems (guarantee the
integrity) using MC. Any existing sample implementations?
#5 HW integration
Is there HW design support kit if someone would like to embedd
MC in Real Time environment using for example PCI Passive Backplane
as base?
Background:
ISV is well known Industrial Solutions provider, and is involved
in project where we plan to replace's some old Real Time systems
with TruCluster based solution. Now we need to address software
and hardware issues regarding performance, availability, reliability
and some other issues. We're staging replacement of Hitachi's
solution here, and customer is deciding between HP and us in couple
of weeks, so all comments are welcome.
What we need now is an acceess to small amount of Real Time control
data between two (or more) systems. Best way to access the data would
be sharing the data in memory between systems and keeping the
information updated in files simultaneously. The amount of information
is only few MB's, and I don't have details on what are the latency
requirements in exchanging this info between systems, but I'd expect
MC to suit the needs well if application will be designed appropriate
way.
Thanks,
-jari
| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 1964.1 | mmap and TCR | NETRIX::"[email protected]" | Pelle Wahlstrom | Thu Mar 20 1997 15:03 | 28 |
| Here is the answer to the DRD questions. For the others somebody else
should repond:
>>#2 mmap(), DRD
>> Can DRD devices be mmap()'d (or LSM/DRD volume)?
No, drd does not support the mmap system call. One of the reasons for this is
that the underlying disk driver (typically the scsi disk driver) doesn't
support
the mmap system call either. Another reason is that disks are not a type of
HW device you want to mmap(). mmap() can work fine on objects cached in memory
(like files) or if you can easily write bytes into the HW (like a Graphics
Adapter). Disks don't work
that way. Accessing a byte => Access a block on the disk => Lousy
performance.
LSM doesn't support the mmap system call either. For the same reasons I
believe.
>>#3 Synch.
>> If DRD/LSM supports mmap(), would DLM be best way to synch things
>> between cluster nodes?
Yes, if the same disk blocks are accessed from two nodes the appropriate way
to synchronize these accesses is DLM.
[Posted by WWW Notes gateway]
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| 1964.2 | thanks and more? | namix.fno.dec.com::jpt | FIS and Chips | Fri Mar 21 1997 07:14 | 25 |
| >No, drd does not support the mmap system call. One of the reasons for this is
>that the underlying disk driver (typically the scsi disk driver) doesn't
>support
Exactly what I was "afraid of", well, nice to get confirmation
anyway, thanks!
So, now we must make a design decision between two things:
- not using mmap() and sharing data between systems
with DRD/DLM combination. [performance in question]
- using mmap() [customer preferred way, perf. issues
involved] on file system and taking care of syncing
copies of file with software.
Any other comments or design considerations? Answers to rest of
the questions?
Specially: Can mmap()'d file to be mapped to MC shared memory
at the same time???
thanks,
-jari
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| 1964.3 | pointers? | 16.181.128.8::jpt | FIS and Chips | Tue Mar 25 1997 12:28 | 6 |
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I'll meet customer in two days, and good answers might be worth
of few servers and multi $M sales...so, whom should I ask...?
-jari
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| 1964.4 | silence of ... | namix.fno.dec.com::jpt | FIS and Chips | Wed Apr 30 1997 06:25 | 10 |
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So, we got the sale, and HP lost!
BUT! Now we really need the help with design issues, please,
give any contacts you think might be able to help. This COULD
be real show case for us if we succeed here now.
Thanks,
-jari
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