On Thu, Jan 31, 2013 at 02:44:12PM +0100, Martin Steigerwald wrote: > Hi! > > Today I converted my /home from Ext4 to BTRFS by reformatting and copying > all over again. > > I created the filesystem with -l 16384 -n 16384 -d single -m single on an > logical volume Intel SSD 320 and mount with compress=lzo,spacecache. Current > state:
The way that compression is implemented in btrfs, compressed files always look fragmented, even if they're not. Basically, each compression block shows up as a single fragment. If the blocks are next to each other, the file's not actually fragmented, but still looks like it to fiemap. [snip] > Except for a highly fragmenting file: > > martin@merkaba:~/.kde/share/apps/nepomuk/repository/main/data/virtuosobackend> > ls -lh > insgesamt 1,2G > -rw------- 1 martin martin 1,3G Jan 31 14:07 soprano-virtuoso.db > -rw-r--r-- 1 martin martin 14 Jan 31 14:06 soprano-virtuoso.lck > -rw------- 1 martin martin 0 Jan 27 17:52 soprano-virtuoso.lock > -rw-r--r-- 1 martin martin 13K Jan 31 10:22 soprano-virtuoso.log > -rw-r--r-- 1 martin martin 0 Jan 27 17:52 soprano-virtuoso.pxa > -rw-r--r-- 1 martin martin 8,0M Jan 31 14:07 soprano-virtuoso-temp.db > -rw-r--r-- 1 martin martin 14K Jan 31 14:07 soprano-virtuoso.trx > > > martin@merkaba:~/.kde/share/apps/nepomuk/repository/main/data/virtuosobackend> > sudo filefrag soprano-virtuoso.db > [sudo] password for martin: > soprano-virtuoso.db: 481 extents found > […] > Now I do not perceive any bottle neck so far and this is an SSD. > > What would be your recommendation: Add autodefrag to mount options or not? For an SSD, probably not worth it. > For now I am inclined to let it run that way and see how it goes. I am a bit > reluctant about autodefrag cause of the additional writes it causes. > > > Well, a direct dd of the file to memory is still quite fast: > > merkaba:/home/martin/.kde/share/apps/nepomuk/repository/main/data/virtuosobackend> > echo 3 > > /proc/sys/vm/drop_caches; LANG=C dd if=soprano-virtuoso.db of=/dev/null bs=1M > 1322+0 records in > 1322+0 records out > 1386217472 bytes (1.4 GB) copied, 5.34167 s, 260 MB/s > > > Another database is the Akonadi database, but I am using PostgreSQL for this > at > the moment which tends to use lots of (smaller) files and due to KDE PIM from > KDE SC 4.4.11 still in Debian, there is no mail metadata in it, just contacts > and > calendar metadata. Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- What do you give the man who has everything? -- Penicillin is --- a good start...
signature.asc
Description: Digital signature
