[dm-crypt] slow read performance, but fast writes?

Milan Broz mbroz at redhat.com
Thu Sep 15 12:45:40 CEST 2011


On 09/15/2011 11:49 AM, Nikolay Kichukov wrote:
> Hi,
> this query is best suited for md-raid mailing list as what you measure:
> 
> dd if=/dev/md3 of=/dev/null bs=1M
> 
> does not involve any decryption. You are reading directly from the md device and there is no matter what is actually there.

heh. I read that as crypt device and it is MD directly, sorry for confusion.
Seems my brain is still in different timezone :)

yes, this test has nothing to do with crypt.

Anyway, it is interesting that the problem is there even without crypt,
perhaps you should ask on linux-raid list then.

for badblock - I guess it just submits all IO from one cpu,
so only one core is used for encryption in fact. There applies the same what I wrote before.

Milan


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