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How to fix "Partition does not start on physical sector boundary" warning?

rated 0 times [ 60] [ 0] / answers: 1 / hits: 299399 / 2 Years ago, sun, november 13, 2022, 11:39:12

I have one HDD on my laptop, with two partitions (one ext3 with Ubuntu 12.04 installed and one swap).

fdisk is giving me the following warning:

Partition 1 does not start on physical sector boundary

What is the cause and do I need to fix it? If so, how?

This is sudo fdisk -l:

Disk /dev/sda: 750.2 GB, 750156374016 bytes

255 testine, 63 settori/tracce, 91201 cilindri, totale 1465149168 settori

Unità = settori di 1 * 512 = 512 byte

Sector size (logical/physical): 512 bytes / 4096 bytes

I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Identificativo disco: 0x5a25087f



Dispositivo Boot      Start         End      Blocks   Id  System

/dev/sda1   *          63  1448577023   724288480+  83  Linux

Partition 1 does not start on physical sector boundary.

/dev/sda2      1448577024  1465147391     8285184   82  Linux swap / Solaris

This is sudo lshw related result:

 *-disk

                description: ATA Disk

                product: WDC WD7500BPKT-0

                vendor: Western Digital

                physical id: 0

                bus info: scsi@0:0.0.0

                logical name: /dev/sda

                version: 01.0

                serial: WD-WX21CC1T0847

                size: 698GiB (750GB)

                capabilities: partitioned partitioned:dos

                configuration: ansiversion=5 signature=5a25087f

              *-volume:0

                   description: EXT3 volume

                   vendor: Linux

                   physical id: 1

                   bus info: scsi@0:0.0.0,1

                   logical name: /dev/sda1

                   logical name: /

                   version: 1.0

                   serial: cc5c562a-bc59-4a37-b589-805b27b2cbd7

                   size: 690GiB

                   capacity: 690GiB

                   capabilities: primary bootable journaled extended_attributes large_files recover ext3 ext2 initialized

                   configuration: created=2010-02-27 09:18:28 filesystem=ext3 modified=2012-06-23 18:33:59 mount.fstype=ext3 mount.options=rw,relatime,errors=remount-ro,user_xattr,barrier=1,data=ordered mounted=2012-06-28 00:20:47 state=mounted

              *-volume:1

                   description: Linux swap volume

                   physical id: 2

                   bus info: scsi@0:0.0.0,2

                   logical name: /dev/sda2

                   version: 1

                   serial: 16a7fee0-be9e-4e34-9dc3-28f4eeb61bf6

                   size: 8091MiB

                   capacity: 8091MiB

                   capabilities: primary nofs swap initialized

                   configuration: filesystem=swap pagesize=4096

These are related /etc/fstab lines:

UUID=cc5c562a-bc59-4a37-b589-805b27b2cbd7 /               ext3    errors=remount-ro,user_xattr 0       1

UUID=16a7fee0-be9e-4e34-9dc3-28f4eeb61bf6 none            swap    sw              0       0

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1 Year ago

answered 2 Years ago amencisiv · Accepted Answer

Your hard disk has Advanced Format 4096-byte sectors to which the partition is not perfectly aligned

This line explains the warning:

Sector size (logical/physical): 512 bytes / 4096 bytes

Your hard disk is one of the newer models which uses the Advanced Format of 4096 bytes per physical sector instead of the older 512 bytes/sector.

These HDDs can still provide a "legacy" emulation of 512 bytes/sector, which is why you see the logical sector size as 512.

In fact, lshw shows it's a Western Digital drive, the first company to switch to AF. They have an extensive page with lots of information on it, which you may wish to look at.

Thus, the warning occurs because partition 1 starts at logical sector 63 = byte 32256, a number not divisible by 4096; in fact it's near the end of the 7th physical sector (position 7.875 to be exact :)

Should you fix it? If so, how? [always backup!]

In theory this sort of partitioning may affect read/write IO rates somewhat, depending on your drive's firmware. If you are happy with the performance now, ignore the warning, and no need to do anything. If not, backup all important data first, and then use Gparted to move the partition so that it starts at 4096-byte sector; setting the start boundary at 1 MiB is an easy way to do it.

Technically, you can set the start to any logical sector which is a multiple of 8, e.g. 64 is good, 256 is good, etc., but 63, 255... are not.