f2fs or ext4

bmike1 · n00b Joined: 05 Sep 2021 Posts: 22

I was wondering what the recommended file system was for for a ssd seeing as they are basically a flash drive. f2fs or ext4?

Goverp · Advocate Joined: 07 Mar 2007 Posts: 2004

I suggest you try searching the forums using Google

mike155 · Posted: Mon Sep 06, 2021 11:12 pm Post subject:

See: https://forums.gentoo.org/viewtopic-t-1130286.html

The_Great_Sephiroth · Posted: Tue Sep 07, 2021 6:14 pm Post subject:

That post is not accurate. Been using F2FS on solid-state media (SATA SSD and M.2 NVME) for ages and it beats the ever-loving pants off of ext4 and even BTRFS. The problem is that people seem to not want to change. ext4 has been around since before solid-state media and cling to it despite it being outdated feature-wise. CoW? No. Snapshots? No. Subvolumes? No. Designed for mechanical or solid-state media? mechanical. It is aging well and I am not against it, but most people simple accept the default (ext4) and assume it is godly without ever trying anything else. I personally left ext4 behind nearly ten years ago. I run BTRFS on mechanical disks and use it for RAID even with SSDs. I use F2FS in single-SSD setups and even on a few USB sticks which are used exclusively by Linux. I even run BTRFS on my Windows rigs to protect my data.

Ext4 is good, but it is dated. Slower than F2FS on solid-state media, far less feature-rich than BTRFS. There are many others which work better also.
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bmike1 · n00b Joined: 05 Sep 2021 Posts: 22

very interesting. well, I was going to go against advice and install it on my thumb drive but was not able to. I'll investigate the whys of this when I get around to putting it on the ssd of the computer I am on as we tip-tap!

Hu · Moderator Joined: 06 Mar 2007 Posts: 21624

Filesystems are difficult to swap out since there is no in-place conversion for most source->destination pairs. Filesystem bugs that cause data loss are seen as very dire for most use cases, so people are generally averse to running a filesystem without a long history of good service. Risk of data loss bugs rises with the complexity of the filesystem, so the more features it offers, the higher the risk that there is a problem somewhere. From the feature angle, people usually acclimate to the currently available features and design their workflows accordingly. Then, when presented with a new feature, such as subvolumes, the first response is to observe that the workflow has no use for the feature. If the workflow has no use for it, then there is no value to switching to a filesystem that offers it. With no added value, but with some theoretical added risk, most people will decide to stay away. To drive adoption of the new generation of filesystems, people need compelling reasons to use those new features.

mike155 · Posted: Tue Sep 07, 2021 7:44 pm Post subject:

pietinger · Posted: Tue Sep 07, 2021 8:26 pm Post subject:

The_Great_Sephiroth · Posted: Wed Sep 08, 2021 3:48 am Post subject:

BTRFS data-loss bugs revolve almost entirely around the yet-to-be-completed RAID 5 and 6. I do not use 5 or 6 anywhere, so I don't care. I normally do 10 or 1. As for the patches, it shows the insane age and lack of maintenance. No patches do not mean perfect. It means lack of development. No standard features of modern file-systems. Heck, by your logic, Fat12 is freaking godly. Seen any patches for it lately? Me either, so it must be good. BTRFS is constantly be added to. New features, better performance, etc etc. I HAVE lost data on ext4 due to bit-rot. I would not have lost the data on BTRFS and I'd have known of corruption on F2FS.

Again, when speaking of losing data on BTRFS it is almost always due to BTRFS RAID 5/6. Filter those out and then show me some data loss. I couldn't find anything about data loss in DUP or SINGLE mode except when a disk died.

I do agree with one thing though. People don't switch if it isn't easy. It doesn't matter how much faster, more secure, or stable something is. If most people can't hit the "easy button" they won't do it. Personally if something came out tomorrow which was as good and fast for an SSD as F2FS is and had the features of BTRFS, I'd wipe and reload. No problem. I'd be down a few days but then I get the best of the two file-systems I use the most.
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Goverp · Advocate Joined: 07 Mar 2007 Posts: 2004

Goverp · Advocate Joined: 07 Mar 2007 Posts: 2004

In answer to the OP, I'm a fan of f2fs; been using it for years on Raspberry Pi's with SD cards, the laptop's SSD drive on which this post is being composed, and a big floorstander's NVMe root filesystem. Apart from one dead SD card in very early days, never had a problem. It seems very good at handling unscheduled power-offs, but you'd expect that as it's a journalling file system

(Oh, and maybe using it on my Android phone; IIUC Google use f2fs for phones, but I've not checked what mine actually uses.)
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pa4wdh · l33t Joined: 16 Dec 2005 Posts: 812

I've been using f2fs on my RPi for a few years now, it works nicely at the sdcard.

All my other disks (actual disks, usb drives and ssd's) are all ext*, not all necessarily ext4 since some are quite old :wink:

. I agree ext* doesn't have all the fancy features, but in my case i don't want or need them.
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Zucca · Posted: Wed Sep 08, 2021 10:26 am Post subject:

f2fs doesn't like sudden power outages, so it fits for laptops pretty well, but for others have UPS and backups.

EDIT: Always have backups, unless you really can afford to lose you data.
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Goverp · Advocate Joined: 07 Mar 2007 Posts: 2004

I happened across the Gentoo wiki article on NVMe, which refers to the one for SSDs. A lot to read about mkfs.ext format options, discard and trim support etc. An advantage of f2fs is that you don't need to worry about these, as it's SSD-aware, and (OK, it's a presumption) should do the right thing by these. The wiki stuff about reducing writes remains valid on f2fs, though IIUC modern NVMes and SSDs have very long lifetimes under normal use patterns.

My 500GB Samsung EVO 970 plus is warranted for writing 300 TB; I've written 1.3 GB in 202 hours power-on time according to smartctl, over the 20 months I've had it installed as rootfs (but not /home, that's on HDD), which gives a lifetime of 300/1.3*20/12=385 years. (I don't trust that 202 hours power-on time; at a guess it should be about 10 times larger).
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pa4wdh · l33t Joined: 16 Dec 2005 Posts: 812

I wouldn't call F2FS SSD aware. It's a filesystem intended for raw flash devices, the ones that usually show op as mmcblk devices. These devices usually don't do the clever stuff modern SSD's do, like wear leveling, sector remapping, etc.. Instead F2FS tries to do those things for you. So having two layers (one in the SSD and one in F2FS) trying to do similar things without knowing what the other does might have a different effect than you think (but you don't know what because the firmware in SSD's is usually not readable for us).
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eccerr0r · Posted: Wed Sep 08, 2021 4:27 pm Post subject:

My (old) android phone uses ext4fs for it's 64G emmc.

Me I keep things simple, modern SSDs were designed to be replacements for regular hard drives and have excellent wear leveling, so run any filesystem you want on it. ext4fs works just fine.

However when it comes to compromised flash storage like SD-cards and raw MTD devices, F2FS is helpful to necessary. I put SD cards in this category only because some of them do not do wear leveling properly.

IMHO flash memory hardware that doesn't or poorly internally wear levels is extremely risky. Unless the erase metadata is kept on an out of band device, if someone cat /dev/zero >/dev/your_f2fs_mtd ... you lose all your wear leveling information and technically your memory device is tough to trust as you'll have no idea how many write cycles are on each page anymore.

All other things being equal it shouldn't hurt running f2fs on a fully wear leveled device. Just that it does have a bit of write amplification as it would be writing unnecessary metadata.
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Zucca · Posted: Wed Sep 08, 2021 6:26 pm Post subject:

eccerr0r · Posted: Thu Sep 09, 2021 1:25 am Post subject:

hmm. then it almost seems it's a solution looking for a problem, unless the main problem is corruption due to power outages which shouldn't happen often and standard SSDs handle with seconds of extra power to ensure things get written in a consistent state. The wear leveling is the main problem that needs to be addressed when using flash, everything else is just gravy.

Perhaps ensuring things that are likely to be deleted together should best be stuck on the same erase page helps, but eventually when it comes to running out of space, you'll still need to do garbage collection because it's difficult to predict what will be deleted together.
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pa4wdh · l33t Joined: 16 Dec 2005 Posts: 812

@Zucca: It seems you are right, maybe f2fs has changed its goals. Every source i can find now also states it's for SSD's.

I'm still struggling why the FS needs to be aware of an SSD while the SSD itself goes through the effort of presenting a "simple" block device and doing wear leveling etc. The only thing left is trim, and opinions on that differ.
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Tony0945 · Posted: Sat Sep 11, 2021 2:34 pm Post subject:

Zucca · Posted: Sat Sep 11, 2021 2:38 pm Post subject:

eccerr0r · Posted: Sat Sep 11, 2021 4:24 pm Post subject:

As a thought question, how much of the hardware should be exposed to the software?

Sounds like people don't want wear leveling details exposed to the software?
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Goverp · Advocate Joined: 07 Mar 2007 Posts: 2004

Hu · Moderator Joined: 06 Mar 2007 Posts: 21624

eccerr0r · Posted: Sat Sep 11, 2021 5:38 pm Post subject:

In this case, the physical hardware has no idea of how many times it gets erased. There must be some microcontroller or something to keep track of erase cycles, so it's a software problem regardless of how it's being looked at - so whether this software should be brought up so it's visible to the OS or not.

Given good underlying firmware that can tell the OS in excruciating detail what's underneath is also a possibility but ignore this for now...
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