ISPPlanet Cache Review Series - Squid 2.3

Do-It-Yourself Caching:
Squid 2.3

by Lisa Phifer VP Core Competence, Inc. [February 28, 2000]

Commercial caching products offer many advantages, ranging from "appliance" installation to stability, feature content to support. But how can an ISP learn about caching first-hand, without trialing or purchasing a commercial product? In our sixth installment of this ISP-Planet series, we try out Squid, a popular open-source cache produced by the ARPA Harvest project and maintained by the National Laboratory for Applied Network Research (NLANR).

Squid 2.3 Free Open Source National Laboratory for Applied Network Research (NLANR) http://squid.nlanr.net

Open Source
Squid is free software that runs on a dozen UNIX operating systems, including BSDI, Solaris, SCO, AIX, HP-UX, and Linux. Squid has also been ported to Windows NT, running under GNU-Win32. We installed Squid on two Linux variants: RedHat 5.0 and LinuxOne 1.2.

Squid is distributed as open source: To download, follow links from the Squid home page. You'll need an ANSI C compiler like gcc. For those uncomfortable with source, a few pre-compiled binaries can be found.

Squid can compile and run on minimal hardware, but experience shows that a stable Squid cache requires at least 128 MB RAM and several GB of disk storage. Performance of course varies widely, affected by many factors: CPU, memory, disk, Squid configuration, and kernel tuning.

The Janet Web Cache Service publishes a hardware sizing paper illustrating real-life examples for Intel-based Squid servers. We first ran Squid on a Pentium 133 with 64 MB RAM, but could not achieve long-term stability. We had no problem running Squid on a Pentium III 500 with 128 MB RAM and 20 GB disk with only 4 GB allocated to cache storage.

Of course, we were only shooting for a stable eval platform, not production-quality performance. The first IRCACHE Bakeoff found Squid to max out at 100 requests per second on a PII 333 with 256 MB RAM and 30 GB storage. We evaluated a newer version of Squid (2.3.STABLE1) but made no attempt to measure its performance.

"Off-the-shelf" Squid lacks the custom file system, optimized kernel, tuned protocol stack, and redundant hardware support provided by commercial cache products. If you plan to deploy Squid, you'll want to start with fast, robust hardware and tweak your config to get the most of out this open source solution. Plenty of physical memory and Fast or Ultra Wide SCSI disks are highly recommended.