Brian, Your remark is completely justified : theory can be limited by some external variables.
For example, we saw there was a limit with "ext2" file system : EXT2_MAX_GROUP_LOADED is used to prevent too much cache bitmaps into memory. As Lustre is based on ext3, is there such a limit with ldiskfs ? If so, we could continue to have bad performance again with big big files on all OSTs (for example). I let Anand tell us if results are better on its benches after a dumpe2fs on every device... Cédric Brian J. Murrell a écrit : > On Tue, 2008-03-25 at 10:37 -0400, Oleg Drokin wrote: > >> You certainly can prefetch that data sooner as a workaround and >> with zero kernel hacking >> required by e.g. doing dumpe2fs on every device with lustre >> backend fs after lustre servers >> are started (it is important to do this after mount, since kernel >> discards all block device data >> on last device close). >> > > Cédric, > > If nothing else, you could use this technique to confirm Oleg's theory > that it is indeed bitmaps being cached that is resulting in your > performance observations. Not that I doubt Oleg's expertise here. It > would just be scientific data to confirm your situation. > > b. > _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
