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
