On 06/07/2010 02:37 AM, Jan Kara wrote: >> With other none checksum fixtures, like RAID5/MIRROR this is not always >> > an option and it becomes keep-constant vs copy. (That is complete >> > workload copy). So for these setups the option is clear. No? > > Is it? You can have enough CPU / memory bandwidth to do the copying while > you need not be comfortable with a thread blocking until IO is finished > when it tries to do a rewrite... > >> I'm glad that you think it is easy/doable to implement. And I'll surly >> test your above receipt. Do you think it would be acceptable as a generic >> per-sb tunable. So for instance an ext3 over RAID5 could turn this on >> and eliminate the data copy? > > Yes, that would be useful. At least so that one can get real performance > numbers... > > Honza Thanks Jan. You have helped me tremendously. I think I can begin to understand now what I need to do. With the workloads I need (HPC), every cycle/memory counts and that the app waits for a rewrite is a good thing, which reminds me that I would want to trace that case so applications could be fixed, tuned. I do understand that for a desktop, that might be just the opposite, so testing is important. Perhaps I'll need help in instrumenting all this. Thanks Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
