copy full system from old disk to a new one

[Reindl Harald]

Am 19.02.2013 19:19, schrieb Gordan Bobic:
> 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

but does not transfer whole RAID setups with all their UUIDs
and detail config and so better wait for SSD's which are not
crippled by get ONE TIME written completly which iw ould
consider as broken hardware

also with dd over ssh the empty space is compressed and not
transferred, with modern CPUs and RC4 cipher this goes up
to 98 MB/second over Gigabit ethernet

before i reinstall the machine eblow whcih exists
more than one time i stay with 2 TB non SSD-disks
and in a few years you can expand the RAID10 to a
spindle with 6x2TB which is fast enough for most
workloads if not all, currently the 4X2 TB RAID10
is reading up to 300MB/sec and writes 150-200 MB/sec

[root at srv-rhsoft:~]$ df -hT
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/md1       ext4   29G  6.4G   23G  23% /
/dev/md0       ext4  485M   38M  447M   8% /boot
/dev/md2       ext4  3.6T  1.7T  2.0T  46% /mnt/data
[root at srv-rhsoft:~]$ df -iT

Filesystem     Type Inodes IUsed IFree IUse% Mounted on
/dev/md1       ext4   1.9M  174K  1.7M   10% /
/dev/md0       ext4   126K   350  125K    1% /boot
/dev/md2       ext4   231M  944K  231M    1% /mnt/data

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