[Solved] FS for USB-flash?

Perfect Gentleman · Veteran Joined: 18 May 2014 Posts: 1256

I got Gentoo installed on USB-flash. USB is formatted in XFS. But lately FS becomes corrupted after doing nothing. Really, I did nothing for a couple of days, and today's morning system became un-pingable.

What's the best FS for headless installation on USB-flash?
or it's bad USB-flash?

NeddySeagoon · Posted: Mon May 01, 2017 8:13 am Post subject:

Perfect Gentleman,

USB Flash is slow since it rarely supports discard or wear levelling.
Journaled filesystems are bad for Flash too.

I use ext4 with the journal turned off on microSD cards, they are Flash.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Perfect Gentleman · Veteran Joined: 18 May 2014 Posts: 1256

I use journaled FS because of power cut which happens rather often.
I used EXT4 without journal couple of years ago, and it was completely destroyed after two power cuts.

NeddySeagoon · Posted: Mon May 01, 2017 10:05 am Post subject:

Perfect Gentleman,

By default, ext4 only journals metadata. A journal replay makes the filesystem metadata self consistent but says nothing about any user data that may be stored on the filesystem.
You can journal everything but that means updates take two writes, once to the journal then to the filesystem.

Journaling is not a magic bullet. You can still corrupt a filesystem with a power cut.
Its usually faster to do a journal replay that a full fsck.

For power cuts you need a UPS, so you can get a clean shut down.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

szatox · Advocate Joined: 27 Aug 2013 Posts: 3503

It's a case where I'd consider f2fs or perhaps some other so called "logging" filesystem. Something that doesn't really have any area for data, and instead stores everything in journal.
They have that nice property that it creates a new point in time view of the filesystem first and tags older views as dirty later, so your previous good version can never be partially overwritten, which in turn makes room for rolling back to the previous known good version in case of failure. Assuming this feature actually works

Perfect Gentleman · Veteran Joined: 18 May 2014 Posts: 1256

there was another blackout. USB FS had lots of errors corrected, but system is bootable and functioning.

Perfect Gentleman · Veteran Joined: 18 May 2014 Posts: 1256

USB-flash died today.

NTU · Apprentice Joined: 17 Jul 2015 Posts: 187

Microsoft says exFAT works great for SSDs and other flash media. Seems legit.

NeddySeagoon · Posted: Thu May 04, 2017 12:16 pm Post subject:

NTU,

exFAT on Linux is depends on FUSE. That makes it slow because of all the context switches.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

chithanh · Posted: Thu May 04, 2017 3:35 pm Post subject:

USB flash drives sometimes have a "pretend to write successfully, but read only garbage" failure mode.

I have one USB flash drive that does precisely this. Copying small files is usually no problem, but copying a large file like an ISO image will cause parts of it to be corrupted (rsync told me it was about 300 KiB corrupted of a 4 GiB file).

See if your USB flash drive corrupts data by filling it with large files, then "echo 3 > /proc/sys/vm/drop_caches", then comparing sha1sum.