Corey Hickey wrote:
Johannes Segitz wrote:
On Tue, Apr 21, 2009 at 3:19 AM, NeilBrown <neilb@xxxxxxx> wrote:
Have you done any testing without the crypto layer to see what effect
that has?
Can I suggest:
for d in /dev/sd[gjk]1 /dev/md6 /dev/mapper/data bigfile
do
dd if=$d of=/dev/null bs=1M count=100
done
and report the times.
tested it with 1gb instead of 100 mb
sdg
1048576000 bytes (1.0 GB) copied, 9.89311 s, 106 MB/s
sdj
1048576000 bytes (1.0 GB) copied, 10.094 s, 104 MB/s
sdk
1048576000 bytes (1.0 GB) copied, 8.53513 s, 123 MB/s
/dev/md6
1048576000 bytes (1.0 GB) copied, 11.4741 s, 91.4 MB/s
/dev/mapper/data
1048576000 bytes (1.0 GB) copied, 34.4544 s, 30.4 MB/s
bigfile
1048576000 bytes (1.0 GB) copied, 26.6532 s, 39.3 MB/s
so the crypto indeed slows it down (and i'm surprised that it's that
bad because i've read
it's not a big hit on current CPUs and the X2 isn't new but not that
old) but still read speed
from md6 is worse than from one drive alone
If it helps, some recent dd benchmarks I did indicate that twofish is
about 25% faster than aes on my Athlon64.
Athlon64 3400+ 2.4 GHz, 64-bit Linux 2.6.28.2
Both aes and twofish are using the asm implementations according to
/proc/crypto.
All numbers are in MB/s; average of three tests for a 512MB dd
read/write to the encrypted device.
read write
aes 69.4 61.0
twofish 86.8 76.6
aes-cbc-essiv:sha256 65.1 56.3
twofish-cbc-essiv:sha256 82.6 73.5
Good info, but was the CPU maxed or was something else the limiting factor?
--
bill davidsen <davidsen@xxxxxxx>
CTO TMR Associates, Inc
"You are disgraced professional losers. And by the way, give us our money back."
- Representative Earl Pomeroy, Democrat of North Dakota
on the A.I.G. executives who were paid bonuses after a federal bailout.
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