Real World Computing
Is fast the new slow?
Picking a brand of PC for your network workstations is starting to resemble picking a good wine for your Christmas dinner - it's just about as public, it can easily become just as embarrassing, and the most obvious big names are by no means the best or smartest choice any more. Unlike a lot of people who are getting all worked up about it, I'm entirely sanguine about the apparent "softening" of the benchmark arms race. It came as no surprise to me at all when both Intel and AMD voluntarily ducked out from the CPU clock-speed arms race and started instead to deploy faster system buses and more off-processor intelligence to extract more bang for the buck. What's far more surprising is when you start to browse the current marketplace and discover what you get nowadays for your money thanks to these innovations.
Let's look at a couple of case studies from the very smallest kind of network - the sort that's going to stir up all kinds of sound and fury during 2008 with the arrival of Windows Home Server - I'm talking about the guy at home with his laptop. Go out today and buy a NAS device from any manufacturer, from the greatest to the smallest, then stack a £350 Vista-powered laptop on top of the box on your way to the checkout, take them both home and the chances are that when you fire them up together their point-to-point network copy speed will be lower than anything you've encountered since about 1996.
What's so irritating is the sheer multiplicity of causes for this appalling performance. First, there's a known bug in Vista that seems linked to the part of the copy dialog that estimates the time remaining for a copy operation (which I detailed here a couple of columns ago); then there are the known incompatibilities between certain NAS models or brands; and then there's the way Windows machines like to talk to their networked hosts. Is it via SMB? Is it via CIFS? Is the password encrypted during the trip it makes down the wire, or is it sent in plain text? What if the far end is using FAT32-formatted drives? (Don't laugh, I've seen them.) Suppose your antivirus package hogs so much RAM your PC starts swapping to the disk it's copying from, just in order to run a scan of the files it's sending down the pipe, which it scanned only the previous evening?
The net result of such multiple, competing and all negative influences is that in my little experiment - using a NAS server with an out-of-the-box fresh Lenovo ThinkPad Z61 containing (cue sound effect of bing-bong BING-BONG Intel jingle) a dual-core Pentium 4 plus a fully bundled installation of Vista Business, and talking across a gigabit network - my best copy speed was down to below 1.5Mb/sec.
Now, I can hardly analyse this problem without following my own advice, as presented to so many readers and clients over the years: namely, to break down the problem into testable chunks and work through it bit by bit. I'll admit that in this example the target end of the copy was very much a worst-case scenario, because my NAS server from Netgear will support extra storage connected via the USB port, and I'd taken advantage of this facility by putting an old laptop hard drive inside a nasty plastic case powered from the USB connector itself, and that's the drive to which my copy was going. However, changing the target of the copy to the NAS's own internal RAID array made next to no difference to the speed.
On the other hand, taking apart the software configuration of the laptop helped quite a lot. As is the case with most of these cheap-end laptops that are sold via TV adverts - in a singular departure from IBM/Lenovo's long-term and honourable history - the Z61 with Vista Business and Norton Internet Security had been sold to me with far too little system RAM to actually operate without swapping like crazy even just to get you logged in. Putting it on a network and attempting to move some data provoked so much swapping activity in the measly 512MB of RAM that the request to pick up a bunch of files and set them moving across the LAN was only the startof a whole series of references to these files. The antivirus software might first want to scan them all while imagining that it's reading its database of virus signatures out of RAM, but it would be wrong because it's actually paging back to the disk database, and laptop disks are famously slow. Getting this cheap laptop up to a specification that could copy files at any acceptable kind of speed required fitting another 2GB of RAM, ditching the overly intrusive antivirus protection, and substituting an alternative file copy utility that isn't the standard Windows Explorer.
