[Asterisk-Users] TDM400P and SCSI/SATA = * noise problems???

[Boris Bakchiev]

We're running asterisk on a pair of 1GB 12mb/s flash cards running on
separate IDE channels. 

We've setup software RAID1 to protect ourselves from failures if any of
the flash cards die.

VoiceMail is stored on a small IDE that is dedicated just for this.

It appears to work quite well. Although we don't have TDM's on our
system.


 
> -----Original Message-----
> From: asterisk-users-bounces at lists.digium.com [mailto:asterisk-users-
> bounces at lists.digium.com] On Behalf Of Damian Funnell
> Sent: Wednesday, 20 April 2005 05:30
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: Re: [Asterisk-Users] TDM400P and SCSI/SATA = * noise
problems???
> 
> Hi Tim,
> 
> Thanks for your post, it's most insightful.  It certainly puts a
pretty
> large dent in my confidence in the TDM for commercial use - imagine if
> there was more than one TDM in a system (especially with a RAID
adapter).
> 
> Running a PABX without hardware RAID 0 is not an option for us, as we
> don't want disk failure to result in the PABX dying, so I guess we are
> going to have to research ways of retarding it somehow.
> 
> Cheers,
> D.
> 
> FFF Managed Technology Ltd
> 60 Cook St
> P.O. 6368 Wellesley St
> Auckland
> t +64 9 356 2911
> f +64 9 358 9070
> m +64 21 415 297
> w www.fff.co.nz
> 
> 
> 
> tmassey at obscorp.com wrote:
> 
> >Yes.  It has to do with latency and bus contention.
> >
> >I've run a TDM board in an IBM Netfinity 5600 server with an IBM
> ServeRAID
> >3L controller (SCSI-U2W).  The big difference, though, is that the
RAID
> >controller was on its own PCI bus, and the TDM card was on its own
PCI
> >bus.
> >
> >With both controllers on the bus, you can have latency issues.  For
> >example, if the RAID controller sets up a DMA of a big chunk of disk,
it
> >owns the bus for that transfer.  If an Ethernet packet is delayed by
50us
> >during that time, nobody cares.  But if the TDM card is delayed, it
most
> >certainly cares:  especially as its generating 1000 interrupts a
second!
> >
> >That's the problem with the TDM cards.  They do *nothing* on the CPU
> side.
> > The CPU has to do *everything*, and it has to do it *immediately*.
When
> >you are using plain-jane IDE, you can tweak the kernel to put the IDE
> >stuff at a low priority.  But when you've got a fancy RAID
controller, it
> >tends to think it's the most important thing in the system.  And as a
> >rule, hard drive I/O usually *is* the most important I/O going on in
a
> >system.  However, in this case, the TDM card trumps that.  And Digium
> >doesn't know how to tweak every last RAID driver in existence for
> >low-priority operation--or even if it's possible.  Hence, the
> >recommendation for IDE.
> >Yet they require PCI 2.2, which eliminates most Pentium III's and
lower!
> >:)
> >
> >I'm still in the midst of testing the TDM cards.  So far, so good, in
an
> >EPIA-based solution and in the 5600.  But I've been through at least
half
> >a dozen different systems before I've found these...
> >
> >Tim Massey
> >
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> >
> >
> >
> >
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