3TB drives and sector alignment, how to partition correctly ? - AVS Forum
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post #1 of 3 Old 10-31-2011, 07:13 AM - Thread Starter
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Greetings,
I am starting to build my Linux file server (mostly for ISO'd blurays) and I am populating it with Seagate 3TB disks (not boot, just data).

I have started to read about the 4K sector alignment problem and I would like very much to use a single 3TB partition. Being a newbie, I am a bit at a loss between the different tools (like old and new fdisk and gparted) and which ones would be the most appropriate.

Can anyone show an example of how I should proceed on partitioning and formatting those shiny new 3TB behemoths ?

I am using Linux Mint 11 (based on Ubuntu 11.04)

For the moment, the Disk tool in Mint11 complains about a 3072 bytes misalignment when I partition directly in Linux. For tests, I partitioned a drive in Windows 7 (GPT, NTFS) and used it in Linux, but I'd rather do the job correctly before starting to fill it with data.

Anyone has crossed that bridge and care to share ?

Thank you
Rudy
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post #2 of 3 Old 10-31-2011, 10:01 AM
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I haven't used any of those drives yet, but this article has the info that you need: http://wdc.custhelp.com/app/answers/...erating-system
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post #3 of 3 Old 11-28-2011, 07:57 AM
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hi

This is what I understand.. what ones needs to do with 4KiB sector drives...

1. Every partition should start at a 4KiB boundary
2. The OS should write in multiples of 4KiB blocks to the fs on those partitions
so that each block stays in one sector or more...

The problem is bad when the HDD manufacturer reports 512byte sectors(physical) when the drive actually has 4KiB physical sectors (like the WD EARS drives)

1.
A simple way is to use
gdisk (gpt fdisk) which does this allignment automatically in the most recent versions...

if you use gnu parted use

-a optimal
or
-a minimal


Don't use fdisk on >3TB drives...as these done support msdos partition tables, gpt table is the way to go...

2. When you create a FS on the newly created partition make sure that the partition size is a multiple of 4KiB(=4096bytes)

eg

mkfs.ext4 -b 4096 /dev/blah...

etc...
I think the latest defaults of mkfs family are 4KiB but just in case...

if you are doing linux raid, then make sure chunk size is multiple of 4KiB, I think the default is 64KiB, but for big drives you can even set the chunk to 128KiB... and then there is some guideline in the mdadm manual for creting the fs based on the chunk size you choose.... etc... etc...


Hope this helps....

Ghat
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