Test results iozone KByte/s

The test first builds a file 4 GByte big (sequential, initial write) and afterwards there will be read from this file (sequential, read). One step later there will be the same on a random basis to see the influence of the access time (random reads/writes). You can compare 4 KByte block size with a text file with only few letters in it. MP3s and movie files conist of 256 KByte and even bigger blocks. If one for example copies 10'000 text files with a size of 25 MByte it takes much longer than copying a 25 MByte movie file. This is becauseauf of the access time which has a big influence with small files. Big files on the other hand aren't affected by the block size.

The following point are of special interest.

• The values reached sometimes are higher the the ones published by the manufacturer.
• Sequential reading values are very close, nearly independent of blocksize.
• Small blocksizes mean a higher load to the SSD especially during reading but the SSD is very fast compared to conventional hard drives.

We created a filesystem with a blocksize of 64 KByte. This because auf the manufacturers information that 32 operations can be executed simultaneously.

We can find the highest values with a blocksize of 128 KByte. Probably this depends on the fact, that a memory cell is erased completely during a writing action. This would also explain the lower writing performance.

Festplatten wurden mit der Zeit dermassen durchoptimiert, dass mittlerweile recht stattliche Werte gemssen werden können. Allerdings kommt es — wie wir gezeigt haben, sehr stark auf die Zugriffszeit an (die übrigens bei dem SSD zwischen 17 und 160 µs liegt), um bei random reads/writes mithalten zu können. Beim sequentiellen Schreiben muss das SSD aber noch passen.