Hi Greg, thanks for your feedback, On Fri, 2011-07-01 at 12:03 -0400, Greg Freemyer wrote: > On Fri, Jul 1, 2011 at 5:30 AM, Werner Fischer <devlists@xxxxxxxx> wrote: > > * 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? > 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. Meanwhile Block sizes have increased up to 2 MiB: 256 pages á 8 KiB for current 25nm NAND from Intel/Micron (which is used also in my SSD) http://www.anandtech.com/show/2928 > 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. I agree, AFAIK this was only true for the very first SSDs on the market. > 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 I agree > 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. For the 25nm NAND from Intel/Micron we know its page size = 8 KiB. For an Ext4 file system with block size 4 KiB (4096 Byte) I could imagine that using stride=2 (2 file system blocks = 8 KiB) and stripe-width=2 (also 2 file system blocks = 8 KiB) would make sense? (just taking the page size into account) > 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. Thank a lot, I already came across them - they've been valuable to me! Werner > 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
