Case for Fast Disks

by Bryon D Beilman
What is the significance of having a fast disk drive in your computer or system vs. having a slow disk drive? It turns out....the difference can be quite significant.

I will discuss my experience in two particular cases, which happen to be the extremes of disk usage. The first is related to laptops and the other being enterprise class storage.

Laptops and disk drives. Laptop drives come in generally a few different types.

So what is the most important factor to look for in a disk drive (and why)?

Get the fastest disk with the most cache you can get. In general the SATA interface is faster, but comparing the more legacy PATA disk performance to SATA, the SATA disks are only slightly faster. What is noticeable is the the transfer rates between a 7200 RPM, 5400RPM and 4200 RPM disk. The top 7200 RPM SATA disk is nearly 2x Faster than a 4200RPM PATA disk. Another noticeable difference is comparing the performance based on cache. The Seagate series with 16 MB of cache has a sustained data rate that is 10Mbps higher (14% ) than that of its 8MB cache cousin. All of this sounds just great, but what does it mean to you, the consumer??

When you boot your operating system, load your Powerpoint presentation or launch your web browser, it loads it from the disk. If you run out of memory, the page file it uses is also on your disk. My personal experience had me upgade the disk of a laptop that I was just about to declare ready for recycling. When I decided to upgrade the disk from 4200 RPM to 7200 RPM, I was overwhelmed with the difference. That laptop is still working today and has alot of life left in it. The Lenovo X40/X41 series is a lightweight laptop that is very popular with road warriors. It, however comes with a 1.8" 4200 RPM disk, that cannot be upgraded to anything faster, because 1.8" disks max out at 4200RPM. The slow disk contributes to many frustrated users and the newer series (X61) now offers 7200RPM 2.5" SATA disks, which makes it comparable to some of the T series models.
When you go to buy a laptop or desktop, do yourself a favor and buy the fastest disk with the most cache available and this will enhance your computing experience.

Server Disks

I am going to write a little about server disks, but there are so many factors that entire companies have been built around providing the fastest and most reliable storage and Server storage could be divided into many blogs to cover the basics.

In Server storage, the concepts are similar, but you have more choices. The definition of a server can vary as well. A 1-4 u server , a fast workstation or even a dedicated file server will all have disks and disk subsystems. Most server class machines use either SATA, SAS, SCSI or Fibre Channel. The speeds vary from 5400 RPM to 15000 RPM disks and like laptops, the cache varies. In servers that are designed to process I/O fast, they typically utilize advanced hardware controllers that use RAID, cache and intelligently balance I/O among disks and many times controllers.
A popular choice in 1/2U servers is currently the SAS (serial attached SCSI) disks that offer small form factor, performance in a hot swappable factor. Hot swappable?? What do you mean by that? Yes, if you utilize some form of RAID (1,3,4,5,6) where there is mirroring or parity to protect the data, the drives can be pulled out while the server is running and replaced without the server being taken down. For those IT professionals reading this, I apologize for stating the obvious, but there are many factors to consider when choosing fast and reliable disk and I/O for your servers.
To throw a monkey wrench in the whole picture, upper level protocols can effect your decision as well. Does it make sense for you to choose a SAN and divide your array into LUNS, or perhaps you need a NAS server to present the same data to multiple hosts. There are best in class for each decision that you need to make. I will dig deeper into server storage and particularly NAS on a later blog. If you have any questions in the mean time?....just ask.