apologies for the re-send - first one bounced On Fri, Jul 1, 2011 at 5:30 AM, Werner Fischer <devlists@xxxxxxxx> wrote: > > Hi, > > * I want to optimize ext4 on my SSD (Intel 320 Series 160 GB). > * There are some sites recommending the use of the -E stride and -E > stripe-width paramaters, like > http://searchenterpriselinux.techtarget.com/tip/Optimizing-Linux-for-SSD-usage > * I know these parameters are useful for RAIDs, but I don't think that > they have any advantages for SSDs. > > Can anybody with deeper ext4 knowledge confirm if I'm right? > > Best regards, > Werner Werner, That article is highly simplistic, and I dare say inaccurate due to the simplifications. For most of us SSDs are magic boxes we push data into and pull data out of. We know the data gets stored on NAND chips and that many (most?) NAND chips have 128KB Erase Blocks. But we have no knowledge of how the data itself is organized. Assuming that a Erase Block contains contiguous sectors is wrong in most cases. There is sophisticated logic going on that is re-mapping the data. Those algorithms are NOT public. We definitely don't know enough to know what stride etc. is optimal. I personally think using 1MB for partition boundaries and a stride which is a multiple of 4KB is probably best, but there really is no good way to know other than performance testing the specific make / model / firmware release you are working with. Here's two wiki pages I wrote that may give you some background: http://en.opensuse.org/SDB:SSD_Idle_Time_Garbage_Collection_support http://en.opensuse.org/SDB:SSD_discard_%28trim%29_support You might want to read them both, then read them both again because the topics depend on each other. And I just noticed this one: http://en.opensuse.org/SDB:SSD_performance I have no idea how accurate the last article is. (I have not read/reviewed it.) Greg -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
