PMDABTRFS(1)

💖 PMDABTRFS 💖

okay bestie, buckle up, we're talking about pmdabtrfs — the btrfs filesystem performance metrics domain agent, aka a PMDA. It lives in section 1 of the General Commands Manual. She's giving very "quietly keeping your filesystem's receipts" energy and honestly? obsessed. 🫶

---

✨ SYNOPSIS ✨

$PCP_PMDAS_DIR/btrfs/pmdabtrfs [-D debug] [-d domain] [-l logfile]

that's it. that's the whole entrance. 💅

---

🌸 DESCRIPTION 🌸

So pmdabtrfs is a Performance Metrics Domain Agent (PMDA, say it with me) and what she does is extract performance metrics from the btrfs filesystem via sysfs — specifically by peeking at /sys/fs/btrfs. nosy in the best way, no cap.

Here's the tea on what she exports, and she does NOT skimp:

• filesystem information (label, sizes, generation, checksum algorithm)
• transaction commit statistics
• space allocation for data, metadata and system block groups
• per-device error statistics
• async discard statistics

All of that. Every crumb. ✨

The metrics are organized into two instance domains:

1. one for btrfs filesystems — keyed by UUID
2. one for devices — keyed by UUID::devid

And because she's thoughtful like that, labels are provided for each instance, including the filesystem UUID, label, and device ID where applicable. 🎀

ok now, a brief description of the pmdabtrfs command line options, because yes there are more than the synopsis showed you:

• -d — the performance metrics domain number, and it must be set to a unique value. unique. don't be out here reusing numbers, that's not the vibe. 🚫
• -l — location of the log file. By default, a log file named btrfs.log is written in the current directory of pmcd(1) when pmdabtrfs is started, i.e. $PCP_LOG_DIR/pmcd. And if the log file cannot be created or is not writable? Then output is written to the standard error instead. she adapts. 💁

---

🌈 INSTALLATION 🌈

The btrfs PMDA requires a Linux system with one or more mounted btrfs filesystems. That's the prerequisite, that's the whole thing. The PMDA reads statistics from sysfs and — good news bestie — does not require root privileges. no sudo, no drama. 🧚

Install the PMDA using the Install script:

# cd $PCP_PMDAS_DIR/btrfs
# ./Install

To remove the PMDA use the Remove script:

# cd $PCP_PMDAS_DIR/btrfs
# ./Remove

install, uninstall, iconic either way. ✨

---

🔥 DEBUGGING OPTIONS 🔥

The -D or --debug option enables the output of additional diagnostics on stderr to help triage problems. Fair warning though: the information is sometimes cryptic and is primarily intended to provide guidance for developers rather than for end-users. so like, it's giving secret dev handshake, iykyk. 💀

debug is a comma separated list of debugging options. Use pmdbg(1) with the -l option to obtain a list of the available debugging options and their meaning. go look, she left you a whole menu.

Debugging options specific to pmdabtrfs are as follows:

• appl0 — warn if the btrfs sysfs directory cannot be found 👀

---

🦋 ENVIRONMENT 🦋

The BTRFS_PATH environment variable can be set to override the default sysfs path (/sys/fs/btrfs) for testing purposes. for testing purposes. we see you. 🙈

---

💜 SEE ALSO 💜

• PCPIntro(1)
• pmcd(1)
• pcp.conf(5)
• pcp.env(5)

---

and that's the whole page, bestie!! 🌟 this manual came to you straight from Performance Co-Pilot (PCP) — she's a PCP girlie through and through, section 1, and she ate. periodt. 💅🎀🫶