On 7/4/13 3:13 PM, "Brad Campbell" [off-list ref] wrote:

On 05/07/13 02:30, Christoph Anton Mitterer wrote:

quoted

Hi.

Well for me personally these are follow up questions to my scenario
presented here: http://thread.gmane.org/gmane.linux.raid/43405

But I think these questions would be generally interesting an I'd like
to add them to the Debian FAQ for mdadm (and haven't found real good
answers in the archives/google).


1) I plan to use dmcrypt and LUKS and had the following stacking in
mind:
physical devices -> MD -> dmcrypt -> LVM (with multiple LVs) ->
filesystems

I have two arrays with dmcrypt on top of MD.
Array 1 is 4 x Seagate 15k SAS drives in a RAID10 f2.
Array 2 is 6 x 240G SSD's in a RAID10 n2.

Array 2 is partitoned. All run ext4.
The CPU is an AMD FX8350. I can max out all arrays with sequential or
random r/w loads. So dmcrypt is not a limiting factor for me.

When I say max out, I run into bandwidth limits on the hardware before
dmcrypt gets in the way.

That is because your CPU has encryption features - the QNAP devices
largely do not; I replaced the CPU in mine with one that had encryption
features because otherwise there was nothing that could bring the
performance above about 80MB/sec


Once I put in a CPU supporting AESNI I could get up to about 500MB/sec -
and this was still not CPU bound