Re: RAID controllers for Postgresql on large setups

[James Mansion <james@xxxxxxxxxxxxxxxxxxxxxx>]

PFC wrote:
>     PCI limits you to 133 MB/s (theoretical), actual speed being 
> around 100-110 MB/s.
Many servers do have more than one bus.  You have to process that data 
too so its not going to be as much of a limit as you are suggesting.  It 
may be possible to stream a compressed data file to the server and copy 
in from that after decompression, which will free LAN bandwidth.  Or 
even if you RPC blocks of compressed data and decompress in the proc and 
insert right there.

>     On your current setup with 15K drives if you need 1 fsync per 
> INSERT you won't do more than 250 per second, which is very limiting... 
Well, thats 250 physical syncs.  But if you have multiple insert streams 
(for group commit), or can batch the rows in each insert or copy, its 
not necessarily as much of a problem as you seem to be implying. 
Particularly if you are doing the holding table trick.

James