I think you need to try running a real benchmark like bonnie++ against both.
For example, you run "time dd" but you don't include the "sync" in the
time...
Daniel Iliev wrote:
Neil Bothwick wrote:
Hello Daniel Iliev,
Actually I'd be glad to read some results from a "Fake RAID-0 vs LVM"
tests. My bet would be that RAID-0 w/o LVM would give the best speeds
Omitting LVM isn't an option, I'd lose all the flexibility that LVM
offers. I don't see why RAID-0 should be necessarily more efficient than
LVM, unless there's something superior about RAID-0's striping
algorithms. I could do some before and after tests, but I'd first have the
reformat the filesystems to remove any effects of fragmentation.
If no one comes up with a good reason for keeping the RAID, I'll get rid
of it, running bonnie++ before and after.
Hi, Neil!
Out of curiosity I made some tests which confirmed my expectations. What
about you - did you have time (and wish) to take some performance
benchmarks? I would be glad to see some additional results.
I'm attaching my tests in file called "bench.txt".
------------------------------------------------------------------------
echo y | mdadm -C /dev/md9 -n2 /dev/sda11 /dev/sdb11 -l0
mkfs.xfs /dev/md9
mkdir /test
mount /dev/md9 /test
dd if=/dev/urandom of=/test.rnd bs=1M count=1500
time cp /test.rnd /test
real 0m44.981s
user 0m0.036s
sys 0m6.967s
sync
time mv /test.rnd /test
real 0m47.514s
user 0m0.047s
sys 0m7.077s
sync
time mv /test/test.rnd /
real 0m53.863s
user 0m0.060s
sys 0m8.885s
mdadm --stop /dev/md9
pvcreate /dev/sda11
pvcreate /dev/sdb11
vgcreate test /dev/sda11
vgextend test /dev/sdb11
vgdisplay | grep 'Total PE'
Total PE 1686
lvcreate -i2 -l1686 -nlogvol test
mkfs.xfs /dev/test/logvol
mount /dev/test/logvol /test
time cp /test.rnd /test
real 1m12.183s
user 0m0.039s
sys 0m9.570s
sync
time mv /test.rnd /test
real 0m51.643s
user 0m0.044s
sys 0m7.275s
sync
time mv /test/test.rnd /
real 1m54.937s
user 0m0.047s
sys 0m9.556s
=================
BOTTOM LINE:
cp /test.rnd /test
LVM: 20.78 [MB/s]
RAID-0: 33.41 [MB/s]
mv /test.rnd /test
LVM: 29.04[MB/s]
RAID-0: 31.56[MB/s]
mv /test/test.rnd /
LVM: 11.11[MB/s]
RAID-0: 27.84[MB/s]
Strange: I repeated the last LVM test because it seemed to me as a low
performance peak, but the result was again very low:
time mv /test/test.rnd /
real 1m27.775s
user 0m0.050s
sys 0m9.813s
which is: 1500/87.775 = 17.089 [MB/s]
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