Messages in this thread | | | Date | Thu, 11 Mar 2010 09:51:07 -0800 (PST) | From | david@lang ... | Subject | Re: RAID + LUKS + LVM performance |
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On Thu, 11 Mar 2010, Matthias Schniedermeyer wrote:
> On 11.03.2010 13:08, Mathias Buren wrote: >> >> Hi, >> >> (please cc me as I'm not subscribed) >> >> I've a friend who's going to set up a fileserver consisting of 8x 1.5TB >> HDDs, an 8-port PCI-E RAID card (Areca ARC-1220 @ >> http://www.areca.com.tw/products/pcie.htm ) etc. >> The plan is create a RAID5 array spanning all the disks, then create 4 >> partitions. These 4 partitions would be encrypted using LUKS (Twofish or >> AES256). >> These 4 encrypted partition would be set up in RAID0 using Linux' software >> (mdadm), then LVM would be used on top of that (one big PV, one big VG and >> a big LV or so). >> >> The reason for this is that kcryptd is not multithreaded (afaik). By having >> 4 encrypted partitions, then md0 on top of them, I'm forcing 4 kcryptd >> processes to run on all four cpu cores whenever something is written to the >> disks, which should improve (encryption) performance. >> >> Is this a good way of doing it, or is there a smarter way? > > The setup you describe would only work with SSDs. HDDs would seek > themselves to death. > > The problem is the RAID-0 over the 4 partitions. At that point you would > need, instead of the 4 partitions, something that is round-robin. So > that the mapping of the (physical) blocks from the upper to the lower > would be effectivly linear/unchanged. > > AFAIK something like that is (currently) not possible.
linux software raid (the md tools) support linear or striped modes for raid0, so what you are looking for is available.
however I think that defeats part of the OPs purpose, which was to try and spread the I/O across all 4 partitions to be able to use multiple cores for the encryption.
David Lang
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