DiskPerf delivers the real deal on drives

Utility talks directly to IO subsystem to profile disk performance

Review by Steve Hammond

DiskPerf, where were you when I needed you?

Actually, that may be stretching it a bit, but our friends at Allegro have brought out a tool that could be helpful to a site like mine that had a series of disk failures just over a year ago.

That tool is DiskPerf, a utility to track performance and IO capabilities for disk devices on both MPE/iX and HP-UX systems. Why, you may ask, would one need such a tool? Disk caching and virtual page storage may mask disk problems, specifically performance issues. DiskPerf avoids those pitfalls by talking directly to the IO subsystem, so it gives us the ‘real deal’ on the drives. Vendors will make claims, but DiskPerf can determine the veracity of those claims. Need to find the slow drive on your machine? DiskPerf will do that. How well is your disk array performing? DiskPerf can help.

About a year ago, my 987SX suffered through a series of hard drive failures. All these failures were tied to the purchase of drives from a vendor whose price was well below the other two bids we received. I am now quite certain the drives were remanufactured although I do not believe they were represented as such. If I had had DiskPerf following that initial failure, I could have monitored the activity on those other ‘suspect’ drives. I might have seen degradation or poorer performance on the drives before they failed over the following six months. But I always said I wanted to spend a night sleeping on the floor of my office...

DiskPerf’s installation is quite simple — so simple, in fact, I could not remember how I had done it and I had to call Allegro to ask them how I had done it! It’s just a restore followed by streaming a job. That’s it. Demos and purchase copies are available on DAT or via Web download.

The product itself is fairly easy to run — all command-line driven, with settings, INFO= strings and even a startup file for regular runs. You can perform the tests on a single drive, a subset of your drives, or all your drives. Furthermore, you can run it with users online, since it performs non-destructive reads to determine drive performance. It performs a variety of tests on several levels to determine the performance of the drives. I monitored my system with Glance while DiskPerf was running and saw no overall performance hit, although my system was not getting heavy user access at the time. DiskPerf’s tests are done to retrieve data randomly, to do multiple same page reads, serial reads, serial reads within a 100Mb chunk of data on the disk, reads where the next read is 1Mb higher than the previous read, and a worst case scenario read (where the next read is the ‘furthest’ page from the current read).

If you tell DiskPerf simply to “test all,” every one of these tests will be performed on every disk on your system. As with any other Stan Sieler-created product, the Help subsystem is extensive and very useful, so you can find anything you need to know about tests or settings with ease. (The Help system is extensive enough that there is no printed manual, and I really saw no need for one.)

The final report at the end of the process gives you the ‘best’ and ‘average’ reads per second for both random and serial access. It also provides the hardware path of the drive, something which can come in handy, since you can never find that hard copy of the configuration when you need it. For regular execution of the program, you can either use INFO= strings in the run command, or you can put the commands in STARTUP.DISKPERF.ALLEGRO, which it reads upon execution.

As for my 987, DiskPerf told me all the drives that I still have questions about seem to be performing within expected tolerances, about within 10 percent of each other on the various tests. Three of my drives are just within the 10 percent factor of the other 15, so I will need to keep an eye on those in the coming months.

One problem is that right now in Stan’s words, “DiskPerf needs a skilled operator to make deductions.” And this is true. You don’t know what each drive should be doing. What if they are all slower than the hardware specifications? You’ll just see they are within the 10 percent range of each other, but that assumes they are working fairly close to spec. That deductions problem is in the process of being resolved, however.

Allegro has asked their beta-testers and other HP e3000 developers who have received the product to send back reports from their drives along with other information on the devices. From this developing knowledge base, DiskPerf will be able to start making some assumptions about the performance of your drives. By determining the drive model and comparing its performance to the knowledge base, DiskPerf will be able to tell the user if a drive is really performing as it should. This feature was not included in the version of DiskPerf that I demoed, but it should be available as you read this.

Another interesting item is the pricing of DiskPerf. The cost is $5,000, or you can rent it for two weeks for $1,500. Allegro realized that this tool is not necessarily something that one would need to run regularly, but could be very useful occasionally — when doing planning for system upgrades and expansions or when attempting to diagnose performance problems. It might be easier to sell your CFO on a one-time $1,500 expenditure with no support costs than the $5,000 hit with subsequent support costs of $750 per year. You can rent DiskPerf for two weeks and determine your problem — and if you decide to buy it within 90 days, the rental price will be credited to your purchase.

After testing it, I would describe DiskPerf as a tool that some of you will need all of the time, and all of you will need some of the time. Allegro realizes this, and has created a fine product with a pricing structure that makes sense for everybody.

Steve Hammond is a system manager for a trade association in Washington, D.C. who has been working with HP 3000s for 18 years and is chairman of the SIGPrint special interest group.