DM-Crypt and RAID

danimalz · 02-19-2009, 07:01 PM

I have 2 drives both are identical.

One has data, the other does not.

each has identical partitions.

I would like to have 1 partition from each drive mirrored, RAID1

I would like this RAID array encrypted.

Is it possible to set up the blank drive with a missing RAID parition, then implement encryption on it, then copy the data from the other drive, then build the raid mirror?

What's the best way to do this?

wsduvall · 02-20-2009, 11:50 AM

I'm a little bit confused at what you want to do. Do you have two empty partitions, do you want to migrate from single drive to RAID? I have encrypted a RAID using LUKS...

Basically, it would go like this: Create and build RAID. Encrypt raid using LUKS (I'm assuming your using LUKS). Then unlock the mount volume. Then create an FS on the unlocked encrypted volume. Hope this helps! Let me know if this helps or exactly what you want.

mostlyharmless · 02-20-2009, 03:00 PM

Quote:

Is it possible to set up the blank drive with a missing RAID parition, then implement encryption on it, then copy the data from the other drive, then build the raid mirror?

What's the best way to do this?

Yes, and it sounds like you answered your own question. That's exactly what I did, setup RAID with "missing", put LUKS on it, set it up to boot in grub as an alternate to the "regular" existing setup, verify that it works, then add the other partition to the RAID, which will, of course, copy over the LUKS etc.

danimalz · 02-20-2009, 03:58 PM

MostlyHamrless - Thank you !

BTW - this is a partition mounted for storage, Im not booting it.

I keep the entire OS on a little cheap disk, boot from that - no raid; re-installing the system is the easist thing to do...

mostlyharmless · 02-20-2009, 06:11 PM

Don't forget to copy (or better yet rsync) your files over to the new RAID BEFORE adding the old disk to the new RAID.

danimalz · 02-22-2009, 12:46 PM

WOW. it is 24 hours and running - i am now using 'cp -a' to copy data to the encrypted partition - CPU is at 100% and the copying is VERY slow. I didnt expect this much overhead.!!!

wsduvall · 02-22-2009, 10:33 PM

Hey danimalz,

What kind of encryption are you using? I use LUKS and I don't have those kinds of slowness. Also, what kind of drives do you use? I like to do

Code:

hdparm -Tt /dev/disk
hdparm -Tt /dev/mapper/unencrypted_mapper

I'm actually not sure how accurate of a benchmark this is but its better than nothing.

mostlyharmless · 02-23-2009, 11:27 AM

My setup isn't slow either; must have to do with your hardware setup, or there's something else going on.

There are a lot of issues getting RAID to be speedy. I's better, for example, for the disks to not be on the same bus, particularly if it's IDE. If the disks are external and USB, well then, they'll be slow, in general.

wsduvall · 02-23-2009, 12:56 PM

Heres my benchmark. The first one shows the speed of the unencrypted drive (SATA, 5000RPM, Laptop) and the second one shows the speed of the encrypted drive:

[wsduvall@Asar ~]$ sudo hdparm -Tt /dev/sda

Code:

/dev/sda:
 Timing cached reads:   2492 MB in  2.00 seconds = 1247.39 MB/sec
 Timing buffered disk reads:  118 MB in  3.03 seconds =  39.00 MB/sec
[wsduvall@Asar ~]$ sudo hdparm -Tt /dev/mapper/
control  home     root     swap     
[wsduvall@Asar ~]$ sudo hdparm -Tt /dev/mapper/home

/dev/mapper/home:
 Timing cached reads:   2468 MB in  2.00 seconds = 1234.74 MB/sec
 Timing buffered disk reads:  112 MB in  3.00 seconds =  37.28 MB/sec

I would be very interested to see the results from your setup.