I think you guys always keep forgetting about the gremlins.
On Tue, Jan 12, 2010 at 1:25 PM, Eli Billauer <[email protected]> wrote: > Etzion Bar-Noy wrote: > > > 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. > > > It crossed my mind that a sequential test was too simplistic. My ideal > test would be a database server running like crazy on the data, but this > is not my application anyhow. I agree that I should test the system > "under load" but I can't really think about a realistic "under load" > scenario for 4 hyperthreaded CPUs. At least not something that I could > test without turning it into a project. So I went for the session below. > > /usr is unencypted. /secret is encrypted. My home directory sits on a > 740 GB ext4 partition, which has seen some activity. /secret and /fresh > are 20 GB, and are pretty untouched. > > The whole system will be reinstalled pretty soon, so I don't care about > being root and fooling around. ;) > > My finding is that encryption still speeds up writes. This is really > weird. I swear that /fresh was created a minute before I used it on this > test, so I suppose it can't be in a better shape. Still, writing to > /secret is faster. The only thing that was slower was removing a lot of > files in one go. > > It's also interesting to note that writing to my home directory was > considerably slower. So even if encryption turns out to have some > impact, other factors (partition size? Fragmentation?) seem to be more > dominant. > > So while I still agree with the concept that encryption must surely slow > down disk writes, my tests show me the contrary. > > Insights, anyone? > Eli > > ---------- Session follows --------------- > > [r...@short eli]# tar -c /usr | { cd /secret/delete-this/ && time tar -x ; > } > tar: Removing leading `/' from member names > tar: Removing leading `/' from hard link targets > > real 5m12.709s > user 0m2.351s > sys 0m31.486s > [r...@short eli]# time rm -rf /secret/delete-this > > real 0m13.319s > user 0m0.180s > sys 0m5.154s > [r...@short eli]# tar -c /usr | { cd /home/eli/delete-this/ && time tar > -x ; } > tar: Removing leading `/' from member names > tar: Removing leading `/' from hard link targets > > real 7m0.826s > user 0m2.344s > sys 0m32.340s > [r...@short eli]# time rm -rf /home/eli/delete-this > > real 0m8.195s > user 0m0.196s > sys 0m5.620s > [r...@short eli]# tar -c /usr | { cd /fresh/delete-this/ && time tar -x ; > } > tar: Removing leading `/' from member names > tar: Removing leading `/' from hard link targets > > real 5m42.639s > user 0m2.332s > sys 0m36.879s > [r...@short eli]# time rm -rf /fresh/delete-this > > real 0m9.612s > user 0m0.203s > sys 0m6.275s > > -- > Web: http://www.billauer.co.il > > _______________________________________________ > Haifux mailing list > [email protected] > http://hamakor.org.il/cgi-bin/mailman/listinfo/haifux > -- Maxim Kovgan
_______________________________________________ Haifux mailing list [email protected] http://hamakor.org.il/cgi-bin/mailman/listinfo/haifux
