Articles: Storage

Bookmark and Share

Pages: [ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 ]

Performance in FC-Test

For this test two 32GB partitions are created on the disk and formatted in NTFS and then in FAT32. A file-set is then created, read from the disk, copied within the same partition and copied into another partition. The time taken to perform these operations is measured and the speed of the disk is calculated. The Windows and Programs file-sets consist of a large number of small files whereas the other three patterns (ISO, MP3, and Install) include a few large files each. The ISO pattern uses the largest files of all.

We’d like to note that the copying test is indicative of the drive’s behavior under complex load. In fact, the disk is working with two threads (one for reading and one for writing) when copying files.

You should be aware that the copying test not only indicates the speed of copying within the same disk but is also indicative of the latter’s behavior under complex load. In fact, the disk is processing two data threads then, one for reading and another for writing.

Both test cycles are interesting here.

The writing results are especially impressive, so we want to discuss them in groups.

Let’s start with the ISO pattern. Its files are so large that cannot fit into the cache memory. As a result, the arrays are all very slow in the first test cycle. If it were not for the problem with the firmware of the LSI SAS3041E-R controller, the single HDD would be able to beat all its 8-disk opponents. In the second test cycle the speeds are 3 to 4 times higher. They should be even higher theoretically, yet these results are anyway good: the previous LSI 8708EM2 model could only deliver a data-transfer rate of 200MBps with RAID0. LSI’s programmers have to work on the firmware more: RAID0 should not lose to RAID50 and be but slightly ahead of other array types.

It is completely different with the Install and MP3 patterns. The files are smaller, so some of them sink right into the cache. This produces a curious effect: the controller delivers almost the same speeds as with the ISO pattern. Moreover, there is a difference between the results of the first and second cycles, but it is not too big. And the first-cycle arrays win in more than half the number of cases. It looks like the large number of random-address requests affects the caching mechanism in some way or another, which provokes a terrible performance hit for large files but can produce some performance gain for small files. If so, the controller’s behavior is no good. Its performance is just too unpredictable.

And finally, the Programs and Windows patterns are all about small files. As a result, the difference between the arrays is almost nonexistent. The arrays of different types and the same-type arrays from the two test cycles all deliver very similar speeds. Frankly speaking, we are quite at a loss trying to comprehend what is going on in the controller.

The inexplicable can be observed in the results again. All the previous results seem to suggest that reading goes in the same way in both test cycles but in two out of the 25 cases there is a difference that cannot be written off as a measurement inaccuracy.

We don’t see high speeds with the ISO pattern: no array is able to overcome a 400MBps barrier. A notable difference between the arrays can be seen with the Install and MP3 patterns: the 2-level RAID10 and RAID50 fall behind the others. This remind us of the multithreaded test where we saw the same standings when the arrays were processing one data thread. The arrays all have similar performance with the other two file-sets.

By the way, take note that the speed of reading of the last two file-sets is much lower than the speed of writing. This must be due to caching. Our test load cannot fully fit into the disk subsystem’s cache, yet the 512 megabytes of cache memory must be accounted for when discussing the results.

The speed of copying files is usually determined by the speed of writing. This is why we see the second-cycle arrays enjoy such a large advantage over the first-cycle ones with the ISO pattern. The MP3 file-set produces a similar picture with one difference: the RAID0 is rather too slow with the ISO files. The 2-level RAID10 and RAID50 are the expected losers in the MP3 pattern.

The arrays produce similar results irrespective of the previous load in the Programs and Windows patterns.

The Install pattern produces weird results. The mixed load (this pattern contains both large and small files) plays a trick on the controller, messing up its performance.

Pages: [ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 ]


Comments currently: 4
Discussion started: 12/07/09 05:06:58 PM
Latest comment: 12/11/15 02:52:41 PM

View comments

Add your Comment