[ ... ] > [ ... ] general purpose filesystems cannot handle well large > groups of small files, [ ... ] >> As can be seen from the time scale in the bottom part, the >> ext4 version performed about 5 times as fast because of a much >> more disk-friendly write pattern. As to 'ext4' and doing (euphemism) insipid tests involving peculiar setups, there is an interesting story in this post: http://oss.sgi.com/archives/xfs/2012-03/msg00465.html on the perils of using 'tar x' as a "test" of something meaningful (illustrated using a much smaller "test" than yours). The telling details was that there was a ratio of 227 times (6 seconds versus 23 minutes) between running 'tar x' without any safety and with most safeties. A ratio of 227 times indicates that there is something big going on, which is that contemporary disk drives have 2 orders of magnitude between bulk sequential and small random "speed" (which is the major reason why «general purpose filesystems cannot handle well large groups of small files»), and that in between one can choose a vast number of different safety/speed tradeoffs (or introduce performance problems :->). Does that means that 'ext4' has "Abysmal write performance" in the 23 minutes case? No, just a different tradeoff. Similarly XFS has had for a long time a mostly undeserved reputation for being "slow" on small-IO/metadata intensive workloads, in large part because traditionally it has been designed to deliver a higher level of (implicit, metadata) safety than other filesystems; for good reasons. Therefore as I argued in other comments the «excessive seeking» you report seems due to me more to storage layer issues and perhaps stricter interpretation of safety by XFS, than to something really wrong with XFS, which is a tool that has to be deployed with consideration. As to that a comparison that does point a finger at the underlying storage system: * In your graphs 'ext4' writes out 2.5GB of small files at around 100MB/s (and with relatively few long seeks on that workload) on an "enterprise" storage system that has 4+2 disks each capable of 130MB/s. * In the 6s "test" I did reported above in a similar situation 'ext4' wrote out 370MB also at not much less than 100MB/s, but on a single "consumer" disk on a much slower destktop. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
