On 25/09/13 16:54, Marc Stürmer wrote: > Greetings fellow Gentooistas, > > at the moment I am doing some testing and evaluating of Btrfs on my own > system. Why? Just because I can and I am curious about it. > > Because I am doing that for evaluation purpose please don't give advise > like "go ZFS" or something like that, thank you. > > Kernel is 3.10.7, the file system is on one hard drive only (SATA). > > And here comes my question: sequential write access seems to be slow as > hell, actually something around like 10 Mbyte/s according to dd's output. > > The same HDD performed under ext4 with around 90 Mbyte/s. > > Command is something like: dd if=/dev/zero of=file.img bs=1G count=150 > > Nothing else is running at the time of writing, no scrub/balance on the > file system or other process eating up much cpu time. > > Mount option is "relatime" only. So is this a well known issue only with > this kernel or generally with this file system at the moment? > > Are there any possible fixes to squeeze better performance out of it or > is this unlikely to happen so that I should better take that into > account of my evaluation and maybe dump it then? > > Thanks in advance. >
How old is the fs? - I am ran into a major slowdown due to COW snapshot fragmentation (VMs on ceph using btrfs) - a known problem. Using that kernel is also giving me an eventual hard lockup if I try and do a recursive defrag (on another system), but the ssd on an apple air defraged fine. btrfs is also seems very sensitive to how full it is. Have you tried a btrfsck? - some errors seem to cause slowdowns as well. BillK
