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-   -   Fdisk shows logical sector size smaller than physical sector size after clonezilla (http://www.linuxquestions.org/questions/showthread.php?t=4175449117)

narnie 02-08-2013 12:56 AM

Fdisk shows logical sector size smaller than physical sector size after clonezilla
 
I bought a new 1tb HD adding it to a 750gb drive. I have a duel boot Windows/Linux Mint Debian setup. I did a clonezilla to copy the 750gb drive to the 1tb drive (it used partclone, I believe).

I did an fdisk /dev/sdb (the newer 1tb drive) to examine the drive. It showed this error:

Quote:

The device presents a logical sector size that is smaller than the physical sector size. Aligning to a physical sector size boundary is recommended or performance may be impacted.
Code:

$ /sbin/fdisk -v
fdisk (util-linux 2.20.1)

Is this a real problem, or is this an fdisk version issue? If it is a real issue, how do I deal with it? Esp with copying over the Windows recovery partition and windows partitions?

I am also wondering about design issues. I would prefer Windows os on the original and my Windows data (user data, etc) on the new drive and the reverse for my Linux, but how hard is it to switch a Windows data volume to another disk (it is already copied onto that disk). The easier road I think would just be let /dev/sda be for Windows and /dev/sdb be for linux, but performance would be better the other way. Thoughts?

Thanks,
Narnie

TobiSGD 02-08-2013 05:10 AM

This is a real problem. Some newer drives (and it will be more in the future) use physical sector sizes of 4KB instead of the older 512B. In order to get full write performance from the disk partitions have to be aligned to those physical sectors. So make sure that the startsector of any partition can be divided by 8.

narnie 02-08-2013 03:20 PM

Quote:

Originally Posted by TobiSGD (Post 4886896)
This is a real problem. Some newer drives (and it will be more in the future) use physical sector sizes of 4KB instead of the older 512B. In order to get full write performance from the disk partitions have to be aligned to those physical sectors. So make sure that the startsector of any partition can be divided by 8.

OK, I wiped the drive and reformated it with SystemRescueCD using gparted mimicking my old HD's partition scheme/sizes. I checked the first sector of each partition and they are all divisible by 8. However, when I do a fdisk, I still get the fdisk warning. Is that OK or should that warning have gone away if my startsector for each partition is divisible by 8 and everything is ok to copy over and put it into production?

Thanks,
Narnie

rknichols 02-08-2013 08:32 PM

If you would post the output from "fdisk -lu" for that drive, someone could give a definitive answer.

narnie 02-09-2013 06:02 PM

Quote:

Originally Posted by rknichols (Post 4887399)
If you would post the output from "fdisk -lu" for that drive, someone could give a definitive answer.

Here 'tis.

Code:

# fdisk -lu /dev/sdb

Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00011318

  Device Boot      Start        End      Blocks  Id  System
/dev/sdb1            2048      86015      41984    6  FAT16
/dev/sdb2          86016    30801919    15357952    7  HPFS/NTFS/exFAT
/dev/sdb3  *    30801920  212738047    90968064    7  HPFS/NTFS/exFAT
/dev/sdb4      212738048  1953523711  870392832    5  Extended
/dev/sdb5      212740096  422453247  104856576    7  HPFS/NTFS/exFAT
/dev/sdb6      422455296  527312895    52428800  83  Linux
/dev/sdb7      527314944  1940940799  706812928  83  Linux
/dev/sdb8      1940942848  1953523711    6290432  82  Linux swap / Solaris

Thank you for any help.

Narnie

rknichols 02-09-2013 09:56 PM

That all looks like it should be just fine.

ulatekh 07-02-2013 11:47 AM

To me, it looks like there's a lot of wasted space in this partitioning scheme. sdb5 starts 2048 sectors past the beginning of sdb4, there's 2048 sectors between the end of sdb5 and the beginning of sdb6, etc. Can anything be done about this?

Right now I'm trying to partition a hard drive with this "issue", and I can't seem to avoid wasting space.

rknichols 07-02-2013 01:18 PM

The 5 sets of 2048 wasted sectors works out to 0.00052% of the 1953525168 sectors on the drive. How much effort do you want to put into reclaiming that?

TobiSGD 07-02-2013 02:58 PM

Quote:

Originally Posted by rknichols (Post 4982732)
The 5 sets of 2048 wasted sectors works out to 0.00052% of the 1953525168 sectors on the drive. How much effort do you want to put into reclaiming that?

Or to give you some other numbers, 2048 sectors are exactly 1 MB, the the wasted space on this 1TB disk is 5MB.

ulatekh 07-02-2013 03:49 PM

If I was willing to accept sloppiness without question, I would be an MS Windows user.
I would at least like to know the source of the unclaimed space, and if there's anything that can be done about it.

sylye 07-03-2013 04:46 AM

ulatekh,

What tools do you use to create the partitions ?

I am doing partition with my new 1.5TB WD15EARS as well, and I used parted which can let me to assign the exact START and END sector number, which at the end I could make no waste of space of my partitioned harddisk. Do you want to take a try with parted ?

ulatekh 07-03-2013 11:57 AM

I was using the fdisk that came with my Fedora Core 17 install/rescue DVD.
I guess I'll have to take another stab at parted...it's been a while since I tried to use that.

rknichols 07-03-2013 09:01 PM

Quote:

Originally Posted by ulatekh (Post 4982827)
If I was willing to accept sloppiness without question, I would be an MS Windows user.
I would at least like to know the source of the unclaimed space, and if there's anything that can be done about it.

The reason is alignment. Modern disk drives with 4KB physical sectors suffer severe degradation in write performance if the filesystem is not aligned to a 4KB boundary, and the erase blocks in SSDs are even larger, perhaps 128KB or 256KB. Current partitioning tools are built to use a 1MB alignment when using sector units (as opposed to legacy cylinder units).

The first partition is always preceded by the single sector MBR, so space must be wasted there to bring that partition back into alignment. Similarly, every logical drive in the extended partition is preceded by a secondary partition table, which again (assuming that the preceding partition uses an integral number of alignment-sized blocks) would misalign them by 1 sector unless some space is wasted to align them properly.

You can use sfdisk with the --force ("Do what I say even if it is stupid") option to place your partitions wherever you like. You could also avoid the use of extended partitions and logical drives by partitioning your disks with GPT, which would only "waste" 68 sectors for the primary and secondary GPTs (34 512-byte sectors each).


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