Yesterday I noticed that the nightly rsync run that backups my root
fs took over 8 minutes to complete. Half a year ago when the backup disk
was freshly formated it only took 2 minutes. (The size of my root fs stayed
constant during this time).
So I decided to reformat the drive, but first took some measurements.
The drive in question also contains my film and music collection,
several git trees and is used to compile projects quite often.
Model Family: Seagate Barracuda Green (AF)
Device Model: ST1500DL003-9VT16L
/dev/sdb on /var type xfs (rw,relatime,attr2,inode64,logbsize=256k,noquota)
/dev/sdb xfs 1.4T 702G 695G 51% /var
# xfs_db -c frag -r /dev/sdb
actual 1540833, ideal 1529956, fragmentation factor 0.71%
# iozone -I -a -s 100M -r 4k -r 64k -r 512k -i 0 -i 1 -i 2
Iozone: Performance Test of File I/O
Version $Revision: 3.408 $
Compiled for 64 bit mode.
Build: linux-AMD64
...
Run began: Thu Aug 1 12:55:09 2013
O_DIRECT feature enabled
Auto Mode
File size set to 102400 KB
Record Size 4 KB
Record Size 64 KB
Record Size 512 KB
Command line used: iozone -I -a -s 100M -r 4k -r 64k -r 512k -i 0 -i 1 -i 2
Output is in Kbytes/sec
Time Resolution = 0.000001 seconds.
Processor cache size set to 1024 Kbytes.
Processor cache line size set to 32 bytes.
File stride size set to 17 * record size.
random random bkwd record stride
KB reclen write rewrite read reread read write read rewrite read fwrite frewrite fread freread
102400 4 8083 9218 3817 3786 515 789
102400 64 56905 48177 17239 26347 7381 15643
102400 512 113689 86344 84583 83192 37136 63275
After fresh format and restore from another backup, performance is much
better again:
# iozone -I -a -s 100M -r 4k -r 64k -r 512k -i 0 -i 1 -i 2
random random bkwd record stride
KB reclen write rewrite read reread read write read rewrite read fwrite frewrite fread freread
102400 4 13923 18760 19461 27305 761 652
102400 64 95822 95724 82331 90763 10455 11944
102400 512 93343 95386 94504 95073 43282 69179
Couple of questions. Is it normal that throughput decreases this much in
half a year on a heavily used disk that is only half full? What can be
done (as a user) to mitigate this effect?
--
Markus
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