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Comment by chris_money202 | Hacker News Reader

They are undoubtly doing this because so many users operate out of /mnt/c with zero clue of that implication.

Would you mind elaborating (for those of us uninformed)

It's difficult to overstate how horrible the performance is.

One example is that if you have a node modules folder on Windows and you try to delete it from WSL it can take 10 plus minutes whereas if you deleted it directly in Windows it would have just taken a few seconds

Also if you try running Next js from files on Windows from WSL it takes minutes for each page to compile to the point that any local development is impossible so you would have to either run the Next JS server on Windows or move the files to WSL

Anything with node_modules takes ages on my Windows machine, whether it is through WSL, Docker or direct, largely in part due to corporate filters, checks, anti-virus and malware protectors and endpoint control.

Although the stuff you mention is true, it is not the only reason. NTFS is just notoriously bad at reading/writing tons of small files.

It also has a lot of problems with locking files that are open by a process, if you have a rogue process reading your node_modules npm install or rm node_modules can hang until that process finishes.

yarn2 keeps dependencies as tarballs instead of extracting them to disk, imported files get loaded from the tarball at runtime. Makes a massive difference in windows.

WSL2 is a VM based on a Windows virtual disk file (VHD). inside that VHD IO is quite fast , a couple degrees worse than native. /mnt/c is how you access your windows files, but it's slow like NFS (socket based). anything needing high IOPS will be dog slow e.g. compiles, file scanning, etc.

the rule of thumb without the newest features is to copy work to/from /mnt/c into $HOME as needed.

/mnt/c is a mounted C: drive in WSL2, that allows WSL2 guests to read/write files on the Windows host.

The mount is fine and speedy enough, but the underlying reads/writes turn into native NTFS reads/writes through Windows. NTFS file API is incredibly slow - high fixed overhead for initial file access.

So patterns like node_modules with many small individual files (or compiling code in general) are much much slower on Windows or WSL2 /mnt/c due to the fixed overhead adding up over a large number of files.

It's a ridiculous problem that has plagued Windows for years.

It's the file system filters that are an issue on Windows. It trades performance for extensibility.

NTFS itself is a fast file system.

eBPF has opened the door to such bloatware on Linux. Previously there was no easy, stable way for enterprise bloatware vendors to maintain complex file and subsystem filter and analytic modules. Now that market is exploding because of eBPF, and it's a big reason there's so much work around growing eBPF's capabilities.

"NTFS itself is a fast file system"

File access is significantly slower on Windows compared to Linux on the same hardware. You can run Linux inside a VM and it will easily beat the host OS in filesystem performance.

If the problem is not NTFS, then it is in how the Windows OS uses it

> If the problem is not NTFS, then it is in how the Windows OS uses it

Isn't that exactly what the comment you are replying to is saying?

This is correct. The flexibility of the file system filter model does have a performance penalty and you will see that across file systems.

This is why 'DevDrive' exists for ReFS, to reduce that penalty (though ReFS comes with it's own, namely in write performance due to journaling).

The model wasn't a big deal back in the day of IDE and SCSI, but it certainly shows on flash storage.

This is what I keep hearing. However, I have never had the good fortune of using a Windows installation where NTFS was allowed to be fast.

Could you expand? I never understood why this was considered acceptable, how is windows filesystem so slow compared to linux?

I am familiar with the issue, doing any sort of ruby development is a nightmare on windows because each require loads a file becoming increasingly slow at boot time

WSL2 operates through a file-level translation layer, not unlike NFS in Linux, which can be a huge performance problem for programs that manipulate lots of tiny files, like git or npm.

Programs that manipulate lots of tiny files are a performance nightmare on Windows even leaving aside the issue of WSL2.

git and npm install are somewhat slower on vanilla Windows, true, but on WSL2 they're downright unusable

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