On Friday 04 March 2011 20:16:05 Xianghua Xiao wrote:
From the data below it appears APACER has a 1MB erasing block instead of the typical 4MB?
Yes, and this is not surprising for an SLC card, although it is the first one I have seen.
Also from the following email(waiting for approval on the list, will forward to you soon), that looks like a 4MB erasing block but is slower than APACER.
Sorry, I need to find the place on the mailing list settings to allow non-members to post, and approve the mails you already sent.
Does open-au-nr with higher number mean the underlying filesystem esp ext4 will do better,
Yes
does that imply multithread parallel writing to some extent?
No, it's not about threads, but about how the data is laid out. ext4 will have to write data, metadata and journal data for many accesses, but these three are normally in different locations on the driver, so you need at least three open segments for the first process that is writing data. If you have other processes that also write to the drive, or one process writing to multiple files, you will need more.
open-au-nr means how many different segments you can use to write to in the same time(so you don't need wait for one segment)?
Yes. The apacer card evidently can write to three segments, but not to six. Can you also try 4 and 5 segments? The interesting number is the maximum.
For the unigen card, it looks like it does not handle random access well, independent of the number of AUs. Best try again without --random.
I probably will recommend APACER over UNIGEN, does that make sense?
Depends on the other measurements.
Arnd