[solved] 4k sectors partitioning question

[optiluca]

Hi all. I have recently purchased a laptop with a 4k sector, "advanced format" drive. I know these drives need to be treated carefully, namely ensuring that all partitions start on a sector multiple of 8 (even though I have seen other values such as 64 and 2048 floating around ). I am unsure however as to how to deal with logical partitions. Does only the "container" partition have to be aligned, or must they all start at sectors multiple of 8? I have also seen constrasting opinions regarding any measures that should be taken when formatting the partitions, with some claims that this operation needs to be "aligned" too. If so, how?

Thanks in advance, and apologies if this has already been asked before. I have seen a few 4k sector threads, but none really addressed these questions.

PS On a side note, should I use ext4 over ext3? Apart from a speeded up integrity check I really can't see anything of interest to a desktop user... Performance does not seem to be clearly better either, at least from what I have seen from Phoronix benchmarks...
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[richard.scott]

You could try this after emerging 'parted':

[optiluca]

The drive currently has a few windows partitions that I would like to keep, so I guess there's no touching the partition table. In any case, I have successfully used fdisk many times over and would be much more comfortable using fdisk & common sense vs. an "automagic" solution which could wreak havoc on my windows partitions. Could anyone confirm that using the "multiple of 8" strategy is indeed correct?

Thanks anyway
_________________
# "Hmm, sounds like your system froze up."
# "I don't know why. It's about 80 degrees in here!"

http://www.rinkworks.com/stupid/cs_mincing.shtml

[frostschutz]

parted --align did not work for me (with an wd15ears drive that reports itself as being 512byte sector based).

In sectors, multiple of 8 works for 4k alignment, since one sector = 512 bytes, 8 sectors = 4k.

The container for the logical partitions does not matter, them partition themselves do. You have to align _all_ partitions that will later actually contain filesystems (or swap).

Or to explain the other way around:

- filesystems should use 4k blocksizes (careful when mkfs.)
- all storage layers below the filesystem (lvm, raid, encryption, partitions, ...) have to be 4k aligned so it ends up 4k aligned on the physical disk itself

I used parted (although manually). Mainly because I'm using GPT partitions, with traditional dos partitions I'd probably make the partition layout with cfdisk, and verify / fix the 4k alignment with sfdisk.

[optiluca]

Ok thank you very much One last doubt however. What blocksize does ext3 normally use? I would have guessed 512 bytes but according to http://linux.die.net/man/8/mke2fs , that is not even an option. How does the filesystem block size relate to the physical size? Is the idea that the filesystem block size must be at least the physical size?

[hielvc]

-b block-size
Specify the size of blocks in bytes. Valid block size vales are 1024, 2048 and 4096 bytes per block. If omitted, mke2fs block-size is heuristically determined by the file system size and the expected usage of the filesystem (see the -T option). If block-size is negative, then mke2fs will use heuristics to determine the appropriate block size, with the constraint that the block size will be at least block-size bytes. This is useful for certain hardware devices which require that the blocksize be a multiple of 2k.


mke2fs -b 4096 ... shoud do it.
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[optiluca]

I figured, I was merely puzzled as to what one does with a standard 512 byte sector considering that is not even an option...

BTW all my preinstalled windows partitions have a starting sector which is multiple of 2048 (with the first partition beginning on 2048 exactly). Why is that?
_________________
# "Hmm, sounds like your system froze up."
# "I don't know why. It's about 80 degrees in here!"

http://www.rinkworks.com/stupid/cs_mincing.shtml

[Hu]

[dmpogo]

Do align beginnings of all partitions on 2048 kbyte (2 MB) boundaries - both extended container, and logical partitions inside *). I find it easiest (I am old-fashioned) to do it with fdisk -u (which shows everything in sectors 512 sectors, you can switch to this view from inside fdisk as well).

*) It is not a 'must' - minimum you should try to align on 4k if it is mechanical drive (the first partition should start at sector 64 then)
and on 512k if it is SSD, but 2048k alignment is becoming standard, both Windows 7 and Mac OSX do this.


Correction: It is 1MB=1024k=2048 sectors alignment not 2MB, so align on 2048 sectors, not kilobytes.

[optiluca]

[dmpogo]

[optiluca]

Ok thanks for confirming that In that case I shall proceed with my installation, which has now encountered an immense circular dependency issue, but that is for another thread...

Thanks to all
_________________
# "Hmm, sounds like your system froze up."
# "I don't know why. It's about 80 degrees in here!"

http://www.rinkworks.com/stupid/cs_mincing.shtml

[kernelOfTruth]

this should answer some questions:
Linux on 4KB-sector disks: Practical advice

with the latest parted (2.2 or 2.3) and gparted (0.7, probably also 0.6.2) you just need to follow the advice in the posted link or

leave it set at "Align to:" MiB (in gparted 0.7) - so that gparted will take care of that for you


sample result:

[Atha]

Hi!

I just faced the same problems with my new Hitachi Deskstar 5K3000 2 TB SATA-III (6Gb/s) 5400rpm hard drive. I already had a 2 TB Western Digital Caviar Green WD20EADS (512b blocks) which didn't need any adjustment/alignment – obviously. So with the Hitachi it is the first time I'm confronted with the new “Advanced Format Technology”.

Since the Hitachi Deskstar reports 512b blocks but realy has 4k blocks, the multiple of 8 rule seemed to be the only way to go.

[Delicates]

[xdarma]