Storage & Filesystem

SMART

These are all safe to run without risk of data loss.

Smart Data can be reset (buyer beware!)

Install:

sudo pacmatic -S --needed smartmontools

List all information:

sudo smart --all /dev/sdx

Run a test (see above for tests available):

sudo smartctl -t long /dev/sdx

Check if test is finished:

sudo smartctl -l selftest /dev/sdx

Check results of test:

sudo smartctl -H /dev/sdx

Badblocks

Run destructive read-write test of entire drive:

sudo badblocks -wsv -b 4096 -c 65536 -o badblocks.txt /dev/sdx

This runs 4 test patterns and then terminates. Block size 4k matches physical block size. Number of blocks = 256 MB at time.

-w = destructuve

-s = show progress

-v = output corruptions to stderr

-b = block size

-c = #blocks

If there is Current_Pending_Sector from SMART, the disk should automatically reallocate them when the sector is ZEROED, i.e. when badblocks is run. You can get the number of times this happens from Reallocated_Event_Count. You generally do not need to mark blocks as bad for the filesystem these days. Run a non-destructive read-write:

sudo badblocks -nsv -t 0 ...

-t = zero it only, do not run other test patterns

TODO: How to identify file, zero it out, and restore from backup. Look at smartmontools wiki.

Performance Test

Partition

Physical sector size = 512b/4kib

SSD Page Size. SSD erasure block size.

Generic - http://codecapsule.com/2014/02/12/coding-for-ssds-part-1-introduction-and-table-of-contents/

Conclusion seems to be stick to 1MiB default first sector.

Bit Rot

Parchive?? - Only for specific files.

cryptsetup --integrityX --sector-size 4096 --label "" --allow-discards (open only)

X = hmac-sha256?--integrity hmac-sha512 and --cipher chacha20-random --integrity poly1305

That detects failures. Use mdadm scrub to be able to fix them.

[0]: https://securitypitfalls.wordpress.com/2018/05/08/raid-doesnt-work/

[1]: https://archive.fosdem.org/2018/schedule/event/cryptsetup/

Levels:

[mdadm - safe disk]

[RAID dev1] [RAID dev2]

[crypt-integrity-AEAD] [crypt-integrity-AEAD]

Not the best idea to use the same disk - performance and disk-failure concerns.

Encyption

Linux fscrypt - fs file encryption could be useful. Once decrypted (key added to kernal keyring), it uses usual unix file permissions to protect access. (ext4, f2fs)

Otherwise dm-crypt.

ext4

-O 64bit,extent,metadata_csum,discard

-m 0 - for non-root drives, no performance impact unless nearly full and running for long time to cause fragmentation

-T largefile - 1MiB files average limit for inodes (for backups).

noatime,lazytime

what is fsck?