[dm-crypt] aes-xts-plain with aes_x86_64 makes my SSD 5x slower than my encrypted HD
marc at merlins.org
Sun Jul 22 21:07:58 CEST 2012
I got a new Samsumg 830 512GB SSD which is supposed to be very high
The raw device seems fast enough on a quick hdparm test:
Timing cached reads: 14258 MB in 2.00 seconds = 7136.70 MB/sec
Timing buffered disk reads: 1392 MB in 3.00 seconds = 463.45 MB/sec <<<<
which is 4x faster than my non encrypted spinning disk, as expected.
But once I encrypt it, it drops to 5 times slower than my 1TB spinning
disk in the same laptop:
gandalfthegreat:~# hdparm -tT /dev/mapper/ssdcrypt
Timing cached reads: 15412 MB in 2.00 seconds = 7715.37 MB/sec
Timing buffered disk reads: 70 MB in 3.06 seconds = 22.91 MB/sec <<<<
gandalfthegreat:~# hdparm -tT /dev/mapper/cryptroot (spinning disk)
Timing cached reads: 16222 MB in 2.00 seconds = 8121.03 MB/sec
Timing buffered disk reads: 308 MB in 3.01 seconds = 102.24 MB/sec <<<<
I used aes-xts-plain as recommended on
gandalfthegreat:~# cryptsetup status /dev/mapper/ssdcrypt
/dev/mapper/ssdcrypt is active.
keysize: 256 bits
offset: 4096 sectors
size: 926308752 sectors
cryptsetup luksFormat --align-payload=8192
the first time, so my offset was 8K, but that did not make a
difference in speed.
gandalfthegreat:~# lsmod |grep -e aes
aesni_intel 50443 66
cryptd 14517 18 ghash_clmulni_intel,aesni_intel
aes_x86_64 16796 1 aesni_intel
gandalfthegreat:~# cryptsetup --version
I know that SSDs are weird and all, but getting a raw device speed of a
mere 23MB/sec down from 463MB/s and compared to 102MB/s for a similarly
spinning drive, is a problem, is it not?
Any suggestions would be appreciated.
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
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.... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/
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