Linux and drives > 2 terabytes; questions.

[Lennart Sorensen]

On Thu, Apr 04, 2013 at 04:06:10PM -0400, D. Hugh Redelmeier wrote:
> I don't remember all the lore to do with >2 TB disks.
> 
> I'm formatting one now as a backup for a MythTV hoard.
> 
> I think that the >2TB disks show sector sizes of 4k now.

Some external drives use 4k sectors.  Drives for internal use rarely do,
since many systems get confused and can't boot from them.

> The previous generation of <=2G drives often had 4K sectors but lied
> to the computer, saying that they had 512 sectors.  This kept dumb old
> systems (Windows and very old Linux) working but it made Linux make
> foolish decisions.  Eventually, Linux changed to take this into
> account.  Foolish folks said Linux couldn't handle 4K sectors but
> in fact what it could not handle was lying.
> 
> I don't know if dumb old BIOSes can boot from disks with 4k sectors.

Not usually.

> I'm using gparted for formatting.  The disk came with an NTFS
> partition (and Windows backup software).  So I rewrote the partition
> table.  I was offered "msdos", meaning the old partition mechanism, so
> I guess that it works OK with 3TB disks if the sectors are 4k.  I
> chose GPT.

GPT is generally a good choice, and doesn't care how big the disk is.

> I'm using ext3 because my old systems might not have solid ext4
> (superstition, not fact).  It is likely that ext2 is just as good for
> my application as ext3.  fsck on a 3TB disk does take a while.
> What is the best filesystem for backing up large files?

ext4 looks pretty good.  I have switch most of my setups to it (which
is easily done in place with some tune2fs magic and an fsck).

> It is unfortunate that gparted can't be told to reduce the number of
> inodes when it is creating a filesystem.  When you are backing up 1.2G
> files (1 hour of TV), the normal proportion of inodes is a waste.  It
> gave me 183148544!  
> 	/usr/sbin/mkfs.ext3 -T largefile4 -L Arthur /dev/sdi1
> gave me 715424.
> 
> I toyed with the idea of devoting a few gigs to make the backup drive
> bootable (with a normal desktop distro) but it is too much bother for
> a "just in case".

-- 
Len Sorensen
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