Question: My SSD (on Windows XP) is working well, however, I get the following strange results from Crystal Mark 2004R3:
236 MB/s for ?sequential read 59 MB/s for ?sequential write168 MB/s for ?random read 512KB151 MB/s for ?random write 512KB 90 MB/s for ?random read 64KB 89 MB/s for ?random write 64KB
How it comes that sequential write is much slower than non-sequential? It’s only about half as fast as sequential write for my standard HDD. I’m quite sure my partition is properly aligned.
Could anybody post their results? Can anybody explain it?
EDIT
On my SSD, there’s a FS with 4kB per cluster and I’m quite sure it’s properly aligned, so each cluster corresponds exactly with one sector (a real 4kB sector, not 512B as Windows thinks). Now I see that according to the wikipedia the page size (i.e., the smallest erasable unit) is “often 4�C8 kilobytes”. The manufacturer doesn’t bother with providing the page size in the datasheet.
At least 1/4 of the disk has never been used, so there should be a lot of free blocks allowing the writes to be fast.
EDIT 2
I forgot to say that my drive is Kinston SV100S2/128G.
Answer: This is only a guess – because XP does not support TRIM, your sequential write is going over blocks that once had data on them and needs to erase them before writing them, this will slow down the write performance of the drive.
When you are performing random writes, the drive might be writing to blocks that are truly blank, resulting in faster performance because the drive does not have to perform an erase operation first.
There are utilities for Operating Systems that do not support TRIM that will go through the drive and erase data on blocks that are not storing information for the filesystem.