Tomasz Chmielewski wrote:
Although the fine mkfs.ext3 manual gives some basic information on how
to do it if you place the whole filesystem on a RAID array, it is not
clear to me how it should be done correctly if I want to create a ext3
filesystem on LVM on RAID-5.
Any helpful hints?
You should be careful with all the alignemnts. Extents should be properly
aligned with - at the very least - stripes, and preferably with whole stripe
width (not always possible though). To check where lvm extents, you can use
i.e.:
dmsetup table
pvs -o+pe_start --units s
losetup and hexedit experiments (silly, but I used to do it like that in the
past, before I realised about other options :o )
If you don't need default 4M granularity, it's nice to increase it (vgcreate
-s option ; I use 256M and 512M sized extents). You can alter the beginning
of the extents with --metadatasize option of pvcreate (overally it always
rounds up to the next 64K multiple). Be sure to verify with one of the
commands above.
Moreover - if you use partitionable raid and create lvm in one of the
partitions, make sure partition is properly aligned as well.
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