Performance in Low-Level Benchmarks

We started out with the simplest of tests. We recorded the drives’ data-transfer graphs in WinBench 99.

Read graph: Intel X25-M SSD on Promise SATA300 TX4302

Well, we got an ideal flat line, just like the theory suggested, but it went at 138,000KBps whereas the manufacturer declared a speed of 250MBps. We trusted Intel and suspected a problem with our testbed. So we recorded the data-transfer graph once again on a different computer. Our testbed for benchmarking with IOMark, our internal program for testing hard disks, is exactly alike, but the tested drive is connected to the ICH7 in it, which is necessary for IOMark to work.

Read graph: Intel X25-M SSD on ICH7

That was quite a different thing. The max speed was now 249,000KBps, which was almost exactly like the declared value. Take note of the considerable fluctuations of speed in the first half of the diagram that lasted for about two minutes and a half. We guess it is the consequence of the address translator adjustment (the SSD had previously undergone a full test cycle in WinBench 99 which was quite a variegated load) in order to ensure maximum performance in this operation mode. This is a normal thing for the translator to do and Intel speaks about that openly. On one hand, two minutes and a half is not too long, especially when the drive eventually delivers maximum performance and ensures a longer service life for the flash memory cells. On the other hand, it is somewhat unpleasant to know that there is something going on inside your SSD that affects its performance. It seems that we must get rid of our notions about the typical behavior of a storage device that we have got used to with hard disk drives.

For comparison, here are the data-transfer graphs of the other drives on the Promise controller:

Samsung SSD on Promise SATA300 TX4302

And a diagram for better readability:

So, even slowed down inexplicably on the Promise controller, the Intel X25-M proves to be faster than any existing HDD including the 15,000rpm model which belongs to the elite of the HDD world. The SSD has no rivals when working at its best on the ICH7 controller. You’d need to unite two HDDs into a RAID0 in order to achieve such a high sequential read speed. We guess this is a most illustrious example of the ten-channel controller’s efficiency. Just compare this to the performance of Samsung’s SSD!

To make sure the speed characteristics were all right we launched our IOMark. This program is intended for HDD tests but it can tell us something about SSDs, too. The X25-M confessed that it had a read buffer with a capacity of 3281KB and knew about look-ahead reading, performing it in 8-sector blocks (8 sectors equals 4KB which is the size of a page in flash memory). But of course we were more interested in speed.

It’s all right with sequential reading here. The neat graph goes at 248MBps even on very large data blocks. Take note that the write speed is even higher than specified by the manufacturer: most of the graph goes at 79MBps.

The speed of working with the buffer is somewhat surprising. Reading from the buffer is slower than the SSD’s sequential read speed (although higher than the speed of the SSD on the Promise controller). Writing from the buffer is performed at a varying speed which jumps very high and then drops to the speed of sequential writing. This must be due to the deferred writing algorithms and the address translator’s operation.

The results of our low-level tests are ambiguous. The SSD proved to be true to its own specifications. Its sequential speeds are indeed very high, the speed of sequential reading being far higher than that of any modern HDD (note that we are talking about sequential operations which were the sore spot of early SSDs, not about random-address operations). On the other hand, the SSD had lower performance on our Promise controller. Frankly speaking, it looks like our controller made the SSD work in SATA-150 rather than SATA-300 mode (the controller chooses the mode automatically without user’s intervention) or the interface bandwidth was too low (but that shouldn’t have been the case as we installed the controller into a PCI-X slot that had a frequency of 100MHz rather than 33MHz). We decided to perform our tests on the Promise controller due to time constraints but we promise that we will soon retest Intel’s SSD under better conditions.