Sorry for answering my own mail, I had a misconception there. I fired various values for dataalignment at cryptsetup and it always chose a value of n*DA >= 4096 sectors. So obviously 4096 sectors seems to be a lower bound I was not aware of. Regards -Sven On Sat, July 18, 2009 09:59, Sven Eschenberg wrote: > Hi Roscoe, > > let me quote from the man page (which of course could be wrong): > > --align-payload=value > Align payload at a boundary of value 512-byte sectors. > This > option is relevant for luksFormat. If your block device > lives > on a RAID, it is useful to align the filesystem at full > stripe > boundaries so it can take advantage of the RAID's geometry. > See > for instance the sunit and swidth options in the mkfs.xfs > manual > page. By default, the payload is aligned at an 8 sector > (4096 > byte) boundary. > ---- > > If it is meant to align payload for raid devices it would be really fatal > if it modifies the value and thus data is not aligned. As far as I > understand it, luks will need at least 8 sectors (4KB) for the header > data. Sine I specificly demanded 2048 sectors (1MB) the value for the > offet should be no problem at all. Further investigation showed, that (my > impression) cryptsetup uses the underlying blockdevice's readahead, which > is certainly the wrong way to determine the payload offset value. > > Regards > > -Sven > > > On Sat, July 18, 2009 03:12, Roscoe wrote: >> On 7/18/09, Sven Eschenberg <sven@xxxxxxxxxxxxxxxxxxxxx> wrote: >>> Hi list, >>> >>> when trying to luksFormat a device with: --align-payload=2048 and thus >>> moving the payload to 1MB from the beginning of the underlying device, >>> luksDump outputs the following: >>> Payload offset: 4096 (?) >>> >>> This does not seem to make any sense. >> >> Perhaps the option means align at a 2048 boundary, thus 2048, or 4096, >> or 6144, etc... >> It I imagine picked the first boundary that wouldn't result in >> overwriting of the keyslots. >> >> -- Roscoe >> >> --------------------------------------------------------------------- >> dm-crypt mailing list - http://www.saout.de/misc/dm-crypt/ >> To unsubscribe, e-mail: dm-crypt-unsubscribe@xxxxxxxx >> For additional commands, e-mail: dm-crypt-help@xxxxxxxx >> >> > > > > --------------------------------------------------------------------- > dm-crypt mailing list - http://www.saout.de/misc/dm-crypt/ > To unsubscribe, e-mail: dm-crypt-unsubscribe@xxxxxxxx > For additional commands, e-mail: dm-crypt-help@xxxxxxxx > > --------------------------------------------------------------------- dm-crypt mailing list - http://www.saout.de/misc/dm-crypt/ To unsubscribe, e-mail: dm-crypt-unsubscribe@xxxxxxxx For additional commands, e-mail: dm-crypt-help@xxxxxxxx
