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MickKi
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Joined: 08 Feb 2004
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 Posted: Fri Mar 22, 2024 7:12 pm Post subject: F2FS discard or nodiscard? |
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Hi All,
I created 2 partitions and formatted them with f2fs. Looking at mount options I see the / partition is mounted with discard and the /home is mounted with nodiscard:
| Code: | ~ # findmnt | grep discard
/ /dev/nvme0n1p2 f2fs rw,noatime,lazytime,background_gc=on,nogc_merge,discard,discard_unit=block,no_heap,user_xattr,inline_xattr,acl,inline_data,inline_dentry,flush_merge,barrier,extent_cache,mode=adaptive,active_logs=6,alloc_mode=default,checkpoint_merge,fsync_mode=posix,compress_algorithm=lz4:5,compress_log_size=2,compress_mode=fs,memory=normal,errors=continue
├─/home /dev/mapper/newhome f2fs rw,noatime,lazytime,background_gc=on,nogc_merge,nodiscard,no_heap,user_xattr,inline_xattr,acl,inline_data,inline_dentry,flush_merge,barrier,extent_cache,mode=adaptive,active_logs=6,alloc_mode=default,checkpoint_merge,fsync_mode=posix,compress_algorithm=lz4:5,compress_log_size=2,compress_mode=fs,memory=normal,errors=continue
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I'm trying to understand why this is the case when both have the same mount options in fstab: | Code: | | defaults,compress_algorithm=lz4:5,noatime 0 0 |
If I try to run discard on /home I get: | Code: | ~ # fstrim -v /home
fstrim: /home: the discard operation is not supported |
Should I force discard or nodiscard on either of these partitions?
What are the recommended fstab mount options for F2FS?
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Mick |
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MickKi
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Joined: 08 Feb 2004
Posts: 1173
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| Posted: Fri Mar 22, 2024 7:31 pm Post subject: |
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Oh! I found this, but I don't know if it is still the case: | Quote: | So in summary for others happening across
this, discard/trim is disabled on LUKS by default; be sure to read the
Arch Wiki page I linked a few replies ago for details and for ways you
can enable it if you understand the security risks of doing so. |
Quoted from the f2fs mailing list.
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CooSee
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Joined: 20 Nov 2004
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| Posted: Fri Mar 22, 2024 7:31 pm Post subject: |
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look at https://wiki.archlinux.org/title/F2FS
| Quote: | Implementation of discard
By default, F2FS is mounted using a hybrid TRIM mode which behaves as continuous TRIM. This implementation creates asynchronous discard threads to alleviate long discarding latency among RW IOs.
It keeps candidates in memory, and the thread issues them in idle time [7]. As a result of this, users wanting periodic TRIM will need to implicitly set the nodiscard mount option in /etc/fstab or pass it to mount if mounting manually. |
| Quote: | | What are the recommended fstab mount options for F2FS? |
you can also try with sys-fs/genfstab <<< make a backup of your current fstab before !
f2fs is not very stable, imho - be careful 
i hope this helps
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MickKi
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| Posted: Sat Mar 23, 2024 9:25 am Post subject: |
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From what I found discard is disabled by default when using dm-crypt LUKS mode, to avoid revealing which sectors are zeroed (discarded) and which are not, so this explains what I observed in the encrypted partition.
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