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#1 2016-09-24 15:27:35

olive
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From: Belgium
Registered: 2008-06-22
Posts: 1,473

Any disatvantage with formating an ext4 without 64bit

Newer ext4 filesystems come with a "64bit" feature that can be disabled with the -O '^64bit' option. Are they any advantage of using the 64 bits options other than increasing the the file size / filesystem limit?

I have now an older ext4 (that was formatted before the 64bits)  and I keep my whole filesystem, including /boot, in a single partition. I use the refind ext4 driver to access it. This driver does not support the 64bit option (I think syslinux has the same limitation). So the solution would be to use a separate /boot partition or simply to continue to use my ext4 filesystem but without 64 bit. My hard disk is well below the limit anyway so maybe I will loose absolutely nothing in doing so.

I do not what to mix the /boot and the efi partition for various reasons.

Last edited by olive (2016-09-24 15:30:02)

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#2 2016-09-24 15:47:55

beta990
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Registered: 2011-07-10
Posts: 205

Re: Any disatvantage with formating an ext4 without 64bit

olive wrote:

Newer ext4 filesystems come with a "64bit" feature that can be disabled with the -O '^64bit' option. Are they any advantage of using the 64 bits options other than increasing the the file size / filesystem limit?

I have now an older ext4 (that was formatted before the 64bits)  and I keep my whole filesystem, including /boot, in a single partition. I use the refind ext4 driver to access it. This driver does not support the 64bit option (I think syslinux has the same limitation). So the solution would be to use a separate /boot partition or simply to continue to use my ext4 filesystem but without 64 bit. My hard disk is well below the limit anyway so maybe I will loose absolutely nothing in doing so.

I do not what to mix the /boot and the efi partition for various reasons.

Just to be safe, have you checked if 64-bit is currently enabled? ($ tune2fs -l /dev/.. | grep 64bit)

Don't think the 64-bit flag will give any performance increase, it will simple allow higher numbers to be used.
Maybe you could take a look at ZFS.

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#3 2016-09-24 15:56:46

olive
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From: Belgium
Registered: 2008-06-22
Posts: 1,473

Re: Any disatvantage with formating an ext4 without 64bit

No 64bits is not actually enabled. However I could reformat it with the feature enabled (it is just of matter of copying all files to an external hard disk, reformat and recopy the files from the external harddisk). But I think I will simply leave things as is. I prefer to stick with ext4 than using ZFS for now.

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#4 2016-09-25 03:28:24

R00KIE
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From: Between a computer and a chair
Registered: 2008-09-14
Posts: 4,734

Re: Any disatvantage with formating an ext4 without 64bit

From 'man ext4'

64bit
              Enables  the  file system to be larger than 2^32 blocks.  This feature is
              set automatically, as needed, but it can be useful to specify  this  fea‐
              ture  explicitly  if the file system might need to be resized larger than
              2^32 blocks, even if it was smaller than that threshold when it was orig‐
              inally  created.   Note  that  some  older  kernels and older versions of
              e2fsprogs will not support file systems with this ext4 feature enabled.

If I'm seeing things correctly then with 4k blocks then this means that this feature is enabled automatically only for partitions larger than 16TiB at format time, otherwise it does not get automatically enabled, so I'd say you are safe.

Force enabling this might cost you something, either speed or some storage space, and definitely costs you compatibility judging from what you say.


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#5 2016-09-25 07:11:05

olive
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From: Belgium
Registered: 2008-06-22
Posts: 1,473

Re: Any disatvantage with formating an ext4 without 64bit

R00KIE wrote:

From 'man ext4'
If I'm seeing things correctly then with 4k blocks then this means that this feature is enabled automatically only for partitions larger than 16TiB at format time, otherwise it does not get automatically enabled, so I'd say you are safe.

Force enabling this might cost you something, either speed or some storage space, and definitely costs you compatibility judging from what you say.

In Archlinux at least it is enabled by default in the file /etc/mke2fs.conf. If that is proper to Archlinux, it is maybe a bad idea and deserve a bug report. Or maybe the man page has not been updated and this policy has changed upstream?

Last edited by olive (2016-09-25 07:11:23)

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#6 2016-09-25 08:57:11

ukhippo
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From: Non-paged pool
Registered: 2014-02-21
Posts: 366

Re: Any disatvantage with formating an ext4 without 64bit

Upstream changed the default in 1.43: http://e2fsprogs.sourceforge.net/e2fspr … .html#1.43

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#7 2016-09-25 12:59:25

R00KIE
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From: Between a computer and a chair
Registered: 2008-09-14
Posts: 4,734

Re: Any disatvantage with formating an ext4 without 64bit

ukhippo wrote:

Upstream changed the default in 1.43: http://e2fsprogs.sourceforge.net/e2fspr … .html#1.43

Then in this case the only options are a separate boot partition(1) or formatting with '-O ^64bit'. There should be no problem in not using the 64bit option but if the option is now forced filesystems without that option will most probably start to get less tested with time and it is possible that a bug appears from time to time.

(1) You could always mount your ESP partition on /boot, that way you shouldn't have any problems.


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