Hi everyone,

I want to pick your brains for hardware suggestions about a Linux-based PostgreSQL 7.4 server. It will be a dedicated DB server backing our web sites and hit by application servers (which do connection pooling). I've hopefully provided all relevant information below. Any thoughts, comments or suggestions are welcome.

Our current server and database:
        Mac OS X Server 10.2.8
        single 1.25GHz G4
        2 GB 333MHz RAM
        7200 rpm SCSI drive for OS, logs
        15k rpm SCSI drive for data

        PostgreSQL 7.3.4
        1 database, 1.1 GB in size, growing by ~15 MB / week
        60 tables, 1 schema, largest is 1m rows, 1 at 600k, 3 at 100k
        Peak traffic:
                500 UPDATEs, INSERTs and DELETEs / minute
                6000 SELECTs / minutes
                90 connections

Performance is fine most of the time, but not during peak loads. We're never swapping and disk IO during the SELECT peaks is hardly anything (under 3MB/sec). I think UPDATE peaks might be saturating disk IO. Normally, most queries finish in under .05 seconds. Some take 2-3 seconds. During peaks, the fast queries are just OK and the slower ones take too long (like over 8 seconds).

We're moving to Linux from OS X for improved stability and more hardware options. We need to do this soon. The current server is max'd out at 2GB RAM and I'm afraid might start swapping in a month.

Projected database/traffic in 12 months:
        Database size will be at least 2.5 GB
        Largest table still 1m rows, but 100k tables will grow to 250k
        Will be replicated to a suitable standby slave machine
        Peak traffic:
                2k UPDATEs, INSERTs, DELETEs / minute
                20k SELECTs / minute
                150 - 200 connections

We're willing to shell out extra bucks to get something that will undoubtedly handle the projected peak load in 12 months with excellent performance. But we're not familiar with PG's performance on Linux and don't like to waste money.

I've been thinking of this (overkill? not enough?):
        2 Intel 32-bit CPUs
        Lowest clock speed chip for the fastest available memory bus
        4 GB RAM (maybe we only need 3 GB to start with?)
        SCSI RAID 1 for OS
        For PostgreSQL data and logs ...
                15k rpm SCSI disks
                RAID 5, 7 disks, 256MB battery-backed write cache
                (Should we save $ and get a 4-disk RAID 10 array?)

I wonder about the 32bit+bigmem vs. 64bit question. At what database size will we need more than 4GB RAM?

We'd like to always have enough RAM to cache the entire database. While 64bit is in our long-term future, we're willing to stick with 32bit Linux until 64bit Linux on Itanium/Opteron and 64bit PostgreSQL "settle in" to proven production-quality.

- Jeff


Jeff Bohmer
VisionLink, Inc.
People. Tools. Change. Community.

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