How to get 5 TB disks for free

A short note, which I was prompted to write by the appearance of this article: “An unexpected find that frees up 20 GB.” Ha! Just 20GB? There is a universal way to release more.

The Linux utility mkfs.ext4 (ext2/ext3/ext4) has a -m option that few people know about. I did not know. And none of my Linux friends knew.

This setting reserves space, in percentage terms, available only to the superuser. So that when ordinary users burn out the entire disk, the demons continue to frantically write their logs without falling. Default value: 5. FIVE PERCENT! That on a 10TB disk gives a crazy figure of 500 gigabytes. Logically, yes! Probably in the early to mid-90s, such a percentage made sense, but obviously not now.

Not only that disk manufacturers juggle giga-gigabytes, invariably selling a volume less than intuitively expected. So also the “tax” on top, at 5%, from the formatting utility! Especially for data disks, where there are no logs and are not expected.

By reformatting my 100TB disks, I got an additional 5TB of disk space, just like that, out of the blue.

Great weekend to everyone!

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