[ale] Realigning a partition with data

[Alex Carver]

In this case the old drive was MSDOS partition with 512b blocks so it's
not 4k aligned.  The file system itself is ext2.  When I imaged the old
drive with ddrescue, I pulled the entire drive in so I'd have the boot
sector and the primary partition (there was only two partitions on the
original drive and one was swap).  I killed off the swap partition then
stretched out the main partition a bit to accommodate the contents of a
second drive that was installed (single partition as well).  I was more
concerned about the block erasing during TRIM in the SSD with unaligned
sectors.

It's mainly used as the network syslog server to record all the logs
from various network devices (cameras, phones, etc.), some data logging
from remote sensors (database), plus I do some internal web applications
with it.  Not really heavy usage.

I've got plenty of old machines floating around with 5.25 floppies or
other storage media.  :)  In rough order of age of all my functional
machines:

Timex Sinclair (tape drive from a TRS-80 is floating around though the
TRS-80 is no longer here)
[Used to have a NorthStar branded CP/M machine with hard-sector 5.25
floppies and integrated green screen -- I taught myself dBase III on it
and cataloged all my electronic parts with it.  It's long gone but it
was functional]
Emerson branded 80286 (this became a modem server though it needs fixing up)
NeXT slab
2x Sun IPXes with external enclosures (one of them is my network GPS clock)
Unbranded (from parts) 386DX with 387 coproc
Packard Bell branded 486SX (now with a 486DX2/66 chip)
Unbranded Pentium II 266 (for experiments)
4x Sun Enterprise 220Rs with dual UltraSPARC II processors (lots of
experiments)
1x Sun SparcStation 20 (RAID server using 2 Sun A1000 arrays)
Unbranded AMD K6 (the topic of conversation)
Toshiba Satellite 1900 series laptop
Averatec laptop
Unbranded Pentium 4 (previous desktop)
3x Raspberry Pi B+
Unbranded Core i7-3770 Ivy Bridge (current desktop)

On 2017-04-23 13:10, DJ-Pfulio wrote:
> I don't think alignment matters on SSDs. They are so fast.
> 
> I've done this with gparted, but always made a full partition backup
> using fsarchiver first.  Didn't need the backup, but ... I'm pretty
> experienced with the tools.
> 
> Also, the underlying file system matters.  XFS/btrfs seem to have the
> most issues.  EXT3/4 seem to be well supported for things like this.  IMHO.
> 
> gparted and parted have always handled alignment issues. I heard that
> fdisk started sometime after they added GPT support (whenever that was).
> I've never used gdisks after seeing all the problems people had with it.
>  Heard that fdisk is safe on GPT again, for the latest distros.
> 
> I have a K2/200 around here somewhere. Keep it for the 5.25in floppy.
> Never know when that will be needed again.  That machine also has an
> Adaptec 2940u SCSI card. ;)
> 
> On 04/23/2017 02:56 PM, Alex Carver wrote:
>> True, I just wondered if there was a way given that parted/resize2fs
>> both worked pretty well with data on a partition (I ddrescue'd the old
>> drive to the SSD then grew the partition).
>>
>> However, after running a couple I/O tests on the drive I'm not going to
>> bother with the realignment.  I'm getting read speeds of about 160
>> MB/sec and write speeds of 116 MB/sec.  Given the age of the machine
>> that's pretty good (AMD K6 with a PCI SATA card and SATA SSD to replace
>> the on-board IDE and old Maxtor drives)
>>
>> On 2017-04-23 05:04, Jim Kinney wrote:
>>> I would not consider realignment safe with data on the sectors that are soon to 
>>> be outside the partition.
>>>
>>> On Apr 23, 2017 2:00 AM, "Alex Carver" <agcarver+ale at acarver.net 
>>> <mailto:agcarver%2Bale at acarver.net>> wrote:
>>>
>>>     Just swapped out a spinning drive for an SSD but I probably need to
>>>     realign the partitions.  Currently everything is in one partition at the
>>>     start of the disk but it's on sector 63.  I can pop the disk out and
>>>     plug it into another machine to do this but I'd like to slide the
>>>     partition over to the right spot (assuming this doesn't affect the boot
>>>     process).  I haven't found a way to do this as nearly every page I find
>>>     talks about having parted align new partitions but not those that have data. 
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