[linux-lvm] Poor LVM dump performance
Ross Vandegrift
ross at kallisti.us
Wed Jan 24 03:33:52 UTC 2007
Hi everyone,
I've run into som substantial read degredation when using dump or tar
to backup filesystems that are stored on LVM2 LVs. Many times in the
past I have seen dump run at speeds approaching block device speeds;
50-60MiB/s, similar with tar.
I'm seeing speeds in the range of 3-4MiB/s when dumping a filesystem.
If I increase dump's blocksize to 128KiB records, speed jumps up to
about 20KiB/s, which is better but still frustratingly slow. Going
to 1024KiB gets me about 28MiB/s.
Is this amount of performance loss expected? My LV is just two SATA
hard disks that I put into a VG. Stupid benchmarks with dd gives me a
raw read speed from the LV of about 60MiB/sec.
Any ideas on what's slowing down dump?
--
Ross Vandegrift
ross at kallisti.us
"The good Christian should beware of mathematicians, and all those who
make empty prophecies. The danger already exists that the mathematicians
have made a covenant with the devil to darken the spirit and to confine
man in the bonds of Hell."
--St. Augustine, De Genesi ad Litteram, Book II, xviii, 37
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