Bill Davidsen wrote: > 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 no encryption 237 131 >> > > Good info, but was the CPU maxed or was something else the limiting factor? To be honest, I didn't check when I benchmarked, but the underlying device is much faster. I added the numbers to the table above. This is for an md RAID-0 of two 1TB Samsung drives. I don't know why the write speed for the RAID-0 is so much slower, except that it's not md's fault; writing to the individual drives is slower, too. I would have investigated more, but, at the time, I really wanted to get my computer operational again. :) That might be lowering my encrypted write speeds a bit relative to the read speeds, but, even if so, I think it would affect the faster of the two ciphers more than the slower--and twofish still leads by a significant margin. Also, to the original poster: Check which crypto drivers in your kernel have ASM implementations loaded: $ grep asm /proc/crypto AES, twofish, and salsa20 are available. -Corey -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
