Sequential IO is very simple, relatively, so that you will hardly feel the performance impact testing it. Test random IO loads with small packets (0.5K-4K) and you will probably feel the performance impact there.
Ez On Mon, Jan 11, 2010 at 7:00 PM, Eli Billauer <e...@billauer.co.il> wrote: > Hello, > > > I suppose that by now some of you have realized that I'm working on > setting up my new computer. ;) > > > The new question is whether I should encrypt the whole hard disk, > including the swap partition (minus, possibly, a read-only mounted > /boot). Just so I don't need to worry in case my computer gets stolen > for worth in metal one day. > > > Mind you, I have a quadcore (the kernel counts 8 CPUs), and I plan on > hardware RAID-5 (Intel P55) with three 1 TB hard disks, not yet > implemented (when I upgrade, I upgrade). RAM sums up to 4 GB. > > > So I ran a small test. /secret is an encrypted partition. My home > directory is not. While the encrypted write ran, I had more or less one > CPU at 100% and seven others doing nothing. The results below are > consistent and repeatable on my computer. Reads to /dev/null take > grossly the same time as write. > > > [...@short ~]$ time dd if=/dev/zero of=/secret/zeros.delme bs=1M count=16k > 16384+0 records in > 16384+0 records out > 17179869184 bytes (17 GB) copied, 158.784 s, 108 MB/s > > real 2m38.822s > user 0m0.015s > sys 0m13.655s > [...@short ~]$ time dd if=/dev/zero of=zeros.delme bs=1M count=16k > 16384+0 records in > 16384+0 records out > 17179869184 bytes (17 GB) copied, 228.711 s, 75.1 MB/s > > real 3m49.069s > user 0m0.010s > sys 0m25.029s > > > Aha! Encryption actually speeds up the write! Well, not really, I > suppose. Maybe it has to do with /secret being untouched until now, and > the cleartext disk being somewhat fragmented by now. > > > But this little test makes me wonder if I pay anything at all for this > (expect for a piece of unused CPU power). If there is any reason in the > world not to encrypt the whole chunk. > > > Inputs are welcome. > > Eli > > -- > Web: http://www.billauer.co.il > > _______________________________________________ > Haifux mailing list > Haifux@haifux.org > http://hamakor.org.il/cgi-bin/mailman/listinfo/haifux >
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