On 29/08/2011 08:35, Alexander Peshkov wrote: > В Вс., 28/08/2011 в 19:14 -0300, Adriano dos Santos Fernandes пишет: >> All, >> >> After I bought a new machine, I reinstalled Ubuntu > 11.04?
Yes. Kernel is 2.6.38. >> in new HDD with ext4 >> filesystem. >> >> While the new machine has much better CPU than the old one, I noticed >> the build being very slow where Firebird was creating databases. >> >> I found that mounting the ext4 partition with barrier=0 parameter >> decreased the performance from more than 2 minutes to less than 50s in >> the build. >> >> But changing this parameter seems to not make ext4 at least safe as >> ext3. So I reverted it and adjust the build to turn FW=off for the >> internal databases. That didn't become fast as barrier=0, but was >> acceptable (around 1 minute). >> >> Now I tried to run tcs and saw it's completely unpractical. So I started >> to test just "create database" performance. >> >> The numbers are around this: >> >> ntfs: 0.2s >> ext3 default (barrier=0): 0.1s >> ext3 (barrier=1): 0.8s >> ext4 default (barrier=1): 2.8s >> >> I removed the O_SYNC flag in posix.cpp and it makes ext4 similar to ext3. >> >> So I have some questions: >> >> Are we doing something wrong? >> > In 'man mount' I see: > Write barriers enforce proper on-disk ordering of journal commits, > making volatile disk write caches safe to use, at some performance > penalty. > > But if barriers are needed just to make journal commits safe on the disk > with write cache turned on this seems to be not directly related with > firebird databases - write cache ON will anyway break firebird database > in case of crash. Or may be this option actually deals with all data on > disk, not only journal? > > Tested CREATE DATABASE on my old box. To avoid disk fragmentation > effects database was always created on new shining partition. > > writecache=OFF > ext3 barrier=0 1.084s > ext3 barrier=1 1.063s > ext4 barrier=0 3.392s > ext4 barrier=1 3.380s > > As expected - FS ignores barriers when cahce is off. > > writecache=ON > ext3 barrier=0 0.388s > ext3 barrier=1 1.023s > ext4 barrier=0 0.410s > ext4 barrier=1 1.884s > > In mode always recommended by us for FB databases, barriers make no > effect. What is interesting to know - does that fance barriers effect > only syslog or all filesystem write safety? Is this "writecache" you're talking the one changeable by hdparm? Here is another funny time: ext4, barrier=1, data=ordered, vmware with file-based disk, guest is Ubuntu 11.04, host is Windows 7 create database time: around 0.45s [compared to 2.8s of same config but non-virtualized] Adriano ------------------------------------------------------------------------------ EMC VNX: the world's simplest storage, starting under $10K The only unified storage solution that offers unified management Up to 160% more powerful than alternatives and 25% more efficient. Guaranteed. http://p.sf.net/sfu/emc-vnx-dev2dev Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
