[clug] 3TB (4k sector) disk question
michael at james.st
Sun Sep 2 03:17:11 MDT 2012
On 01/09/2012, at 6:49 PM, Eyal Lebedinsky wrote:
> Today I bought a 3TB disk, which originally was in a USB3 case (now out of it).
> When introduced linux (as bare SATA) it seems that a sector size of 512B is used,
> and the disk size is limited.
> 'hdparm -I' knows that this is a native 4k disk:
> Model Number: ST3000DM001-9YN166
> Logical Sector size: 512 bytes
> Physical Sector size: 4096 bytes
> Logical Sector-0 offset: 0 bytes
> device size with M = 1024*1024: 2861588 MBytes
> device size with M = 1000*1000: 3000592 MBytes (3000 GB)
> However parted thinks otherwise (I created one large GPT partition):
> # parted /dev/sdi
> GNU Parted 3.0
> Using /dev/sdi
> Welcome to GNU Parted! Type 'help' to view a list of commands.
> (parted) print
> Model: ATA ST3000DM001-9YN1 (scsi)
> Disk /dev/sdi: 2199GB
> Sector size (logical/physical): 512B/512B
> Partition Table: gpt
> Number Start End Size File system Name Flags
> 1 1049kB 2199GB 2199GB ext2 primary
> Note the line 'Sector size (logical/physical): 512B/512B'.
> How do I make linux use 4k sector size? Or is there a jumper
> on the disk? Or a special SATA command to configure the disk?
> Also, should GPT not be able to create very large disks even with 512B
> sectors, using the 64bit internal pointers/sizes/etc.? Where is the
> disk size limit coming from?
If you knew enough to partition it GPT you probably know this
but I hope it's worth putting put for the list.
The 2 TB limit is inherent in Master Boot Record (MBR/MSDOS) partitioning.
The field that delimits a partition doesn't have enough bits to describe anything bigger.
Either it's not done in terms of logical blocks or you can't change that anyway.
Modern disks actually work in 4 KB blocks, but present logically as 512 Byte blocks.
If you partition a disk NOT on 4 KB boundaries; expect 10 x less performance.
This is explained quite well here: http://www.rodsbooks.com/gdisk/
BTW Rod's gdisk partitioning tool is quite a groovy little utility.
Acts like fdisk, writes GPT partition tables.
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