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
[EMAIL PROTECTED] 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
_______________________________________________ Asterisk-Users mailing list Asterisk-Users@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
_______________________________________________ Asterisk-Users mailing list Asterisk-Users@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
