I’ve been needing a serious evaluation of my backup habits. One area is mixing my storage media for longer-term backup. Up until now, I’ve been using DVD’s, but given the hundreds of gigabytes of data I can create in a month or two, and questions regarding long-term storage of writable DVD media, I’ve begun delving into the possibility of using hard drives as part of an overall strategy. But the world of external drives has become exceedingly complicated. Firewire (IEEE-1394), USB 2.0, and more recently SATA/ESATA.
The performance rating of these interfaces are 400 mb/s for 1394a and 800 mb/s 1394b, 480 mb/s for USB 2.0, and 1500 mb/s for SATA 1 and 3000 mb/s for SATA 2. But what are their real-world performances like? The following is the first part of my exeriments on performance
1. The computer - Macbook pro - USB 2, 1394a, Express card for external SATA, internal SATA drive
2. External Firewire/USB 2.0 drive with a 250 GB IDE drive.
3. External SATA 1/USB 2.0 drive case with a 320 GB SATA drive.
I used a typical directory for me, 17.35 GBs, and copied from one drive to the other several times using a shell script. Although I’m mac based, none of these files required resource forks so no special handling was required.
Here are the results of copying back and forth to the mac’s internal drive. The figure below shows the copy time in seconds (best results are SHORTER).
Not surprisingly, the SATA interface performed the best. USB 2.0 performed the worst. Generally, the hardware limitations of the mac’s internal workings are a major factor here, but the results are inline with other results out there on the web. The other limitation is the external drives themselves. Keep in mind that most drives can only write about 30-80 MB/s and the best performer here is only about 230 mb/s, or about 30 MB/s (note that this speed is far far slower that each of the interface’s ratings).
The second experiment is copying external drive to external drive. Since I only have two cases and limited USB 2.0 ports, I was limited in the experiment. Here are the copy times in seconds (best results are SHORTER):
Again, USB 2.0 is the slower of the interfaces. Interestingly, the copy speed to the SATA drive from the Firewire drive is relatively fast: 293 mb/s, or about 37 MB/s; this is the fastest copy speed of the experiment, and it was approaching the 400 mb/s for the firewire interface. I consider that a very good result for Firewire along with SATA.
This first experiment show that my purchase of a SATA1/USB combo case was probably not the best solution - a case that had SATA1 or 2 and firewire would have been far better for my needs. USB 2.0 as a solution is clearly not good enough for me.