Re: High end server and storage for a PostgreSQL OLTP system

Jim C. Nasby wrote:
> On Tue, Feb 01, 2005 at 07:35:35AM +0100, Cosimo Streppone wrote:
>
>>>You might look at Opteron's, which theoretically have a higher data
>>>bandwidth. If you're doing anything data intensive, like a sort in
>>>memory, this could make a difference.
>>
>>Would Opteron systems need 64-bit postgresql (and os, gcc, ...)
>>build to have that advantage?
>
>
> Well, that would give you the most benefit, but the memory bandwidth is
> still greater than on a Xeon. There's really no issue with 64 bit if
> you're using open source software; it all compiles for 64 bits and
> you're good to go. http://stats.distributed.net runs on a dual opteron
> box running FreeBSD and I've had no issues.

You can get 64-bit Xeons also but it takes hit in the I/O department due
to the lack of a hardware I/O MMU which limits DMA transfers to
addresses below 4GB. This has a two-fold impact:

1) transfering data to >4GB require first a transfer to <4GB and then a
copy to the final destination.

2) You must allocate real memory 2X the address space of the devices to
act as bounce buffers. This is especially problematic for workstations
because if you put a 512MB Nvidia card in your computer for graphics
work -- you've just lost 1GB of memory. (I dunno how much the typical
SCSI/NIC/etc take up.)