On 19/02/2013 17:48, Heinz Diehl wrote:
On 19.02.2013, Reindl Harald wrote:
i can not remember when the last ext3/ext4
had 512 bytes blocksize
[....]
Most of the "conventional" harddisks have a sectorsize/blocksize of
512/512. All the newer and bigger WD/Seagate drives and SSDs are using
"advanced format", which means 512/4096.
To support this, there are two factors which must be present:
1. Proper alignment to 4k block boundaries
2. A filesystem on top which supports 4k blocksize
If you use "dd" to raw-copy a 512/512 drive to a newer WD/Seagate or a
SSD, this will result in misalignment (even if your FS supports the 4k
blocksize) causing huge performance loss.
To avoid this, you'll have to create proper aligned partitions on the
new drive first, formatted with a FS supporting 4k blocksize,
and copy the data the "traditional" way, e.g. using cp, rsync and brothers.
To ensure proper alignment it is sufficient to manually partition to 4KB
boundaries and then dd individual partitions over (as opposed to the
whole disk in one transfer). Of course, mkfs + [cp | rsync | tar] will
be much more efficient as it only transfers the files, rather than also
the empty space.
Gordan
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