VDOCALCULATESIZE(8)

🦋 VDOCALCULATESIZE(8) — the vibe check 🦋

okay bestie, so this is a page from the System Manager's Manual, and it's about vdocalculatesize — yes, all lowercase in the title, we love her anyway. She's your girl for figuring out how much space and memory your VDO setup is gonna eat. no cap ✨

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💖 NAME 💖

vdocalculatesize — Calculate VDO space and memory usage

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✨ SYNOPSIS ✨

vdocalculatesize [options...]

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🌸 DESCRIPTION 🌸

vdocalculatesize calculate VDO space and memory usage. That's literally it, that's the whole job description, and she does it flawlessly. 💅

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🎀 OPTIONS 🎀

okay so here's the whole menu, and yes we're going through every single one, because bestie deserves the full tea ☕

• --help — Print help message and exit. The "hey I'm new here" button. She'll tell you what's up and then dip. 👋
• --block-map-cache-size=blocks — Size of the block map cache, in 4K blocks. Note that unit bestie: 4K blocks, not MB, not vibes.
• --logical-size=MB — VDO logical size. (yes, in MB, she said what she said.)
• --physical-size=MB — VDO physical size. (also MB, keeping it consistent, we stan.)
• --slab-bits=bits — Set the free space allocator's slab size to 2^bits 4 KB blocks. bits must be a value between 13 and 23 (inclusive), corresponding to a slab size between 32 MB and 32 GB. The default value is 19 which results in a slab size of 2 GB. This allocator manages the space VDO uses to store user data.

The maximum number of slabs in the system is 8192, so this value determines the maximum physical size of a VDO volume. One slab is the minimum amount by which a VDO volume can be grown. Smaller slabs also increase the potential for parallelism if the device has multiple physical threads. Therefore, this value should be set as small as possible, given the eventual maximal size of the volume. 🧚 tl;dr: go small, but not so small you cap out your future glow-up.

• --slab-size=MB — set slab-size directly instead of using --slab-bits. This option is mutually exclusive with --slab-bits. PICK ONE. you cannot have both, they are not compatible besties, it's giving toxic ex energy. 💀
• --index-memory-size=GB — Specify the amount of memory, in gigabytes, to devote to the index. Accepted options are .25, .5, .75, and all positive integers. So quarters and whole numbers only — no chaotic .333 nonsense, she has standards. 👑
• --sparse-index — Specify whether or not to use a sparse index. (a yes/no situation, very demure, very mindful.) 🎀

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🌈 EXAMPLE 🌈

here's her serving a full look, copy-paste this exact line and it'll do the thing:

vdoCalculateSize --physical-size 600G --slab-bits 22 --logical-size 2T --index-memory-size 1 --block-map-cache-size 32768

and yes, the example spells it vdoCalculateSize with the capitals while the command itself is lowercase vdocalculatesize — that's just how the original rolls, we don't question it, we respect it. 🙈

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🔥 SEE ALSO 🔥

vdo(8). go read that one next, she's the main character and this one's her bestie. 🫶

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and that's the whole page, bestie! this cutie was brought to you by Red Hat, dated 2025-02-24, and she's iconic for it. mwah 💖💅✨