On Monday 24 March 2008, Evgeniy Polyakov wrote: > Hi. > > During stress iozone test I got folowing in the dmesg: > btrfs: sdb1 checksum verify failed on 339968 wanted 0 found 4DF48705 > from_this_trans 0
These are harmless for now, there is a small window where a buffer can change while it is being written (making the csum invalid). It is slated to be fixed after the multi device code goes in. > > Performance degraded to hell for this test (8gb file, automatic iozone > mode, probably during random read test). I'd have to see all the test details to explain performance problems. I would expect that once you do a series of random writes to the file, sequential reads are going to be painfully slow. For that kind of database workload, you'll want to mount with -o nodatacow. Since iozone lays out the file once in the beginning, performance will definitely suffer after it does a random write run. > > Filesystem was made with -l 4k -n 4k options and mounted with > noatime,nodatasum,ssd options. > > Single 266 gb scsi disk. > Any additional details? The ssd mount option assumes that reads are seek free. It will be optimal for postmark, which only does random reads and never does sequential reads, but it will be slower for most other benchmarks. -chris _______________________________________________ Btrfs-devel mailing list [email protected] http://oss.oracle.com/mailman/listinfo/btrfs-devel
