PCP-DMCACHE(1)

💅 PCP-DMCACHE — report on logical storage device caches

okay bestie, welcome to the pcp-dmcache page 💖 (it lives in the General Commands Manual section of the PCP docs, iykyk). also known as pcp-lvmcache, and we're gonna talk about why they're literally the same thing. buckle up 🎀

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✨ NAME ✨

pcp-dmcache, pcp-lvmcache — report on logical storage device caches 🌸

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🦋 SYNOPSIS 🦋

pcp [pcp options] dmcache [-iRV?] [device ...]

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👑 DESCRIPTION 👑

pcp-dmcache spills the tea on what any configured Device Mapper Cache targets are up to. the info it reports includes:

• device IOPs 💫
• cache and metadata device utilization
• hit and miss rates and ratios — for both reads and writes — for each cache device

pcp-lvmcache (that's Logical Volume Manager cache, for the uninitiated) is an exact synonym for pcp-dmcache (Device Mapper cache). same tool, different name, iconic behavior honestly 🫶

by default, pcp-dmcache reports on all available cache target devices — one line each, per sample 🧚 but no cap, you can restrict it to specific devices by listing them on the command line.

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🌈 OPTIONS 🌈

so when you invoke this through the pcp(1) command, a whole squad of pcp options becomes indirectly available:

• -h/--host
• -a/--archive
• -O/--origin
• -s/--samples
• -t/--interval
• -Z/--timezone

…and several other pcp options too 👀. for a complete description of all of those, go read PCPIntro(1) — it's giving reference material, bestie.

now the additional command line options that are special to pcp-dmcache:

• -i, --iops — displays total read and write operations instead of the default cache hit ratio 🔥
• -R, --repeat — changes the frequency at which the column heading is displayed. by default, a header shows up after every tenth sample ✨
• -V, --version — display version number and exit. short and sweet 💅
• -?, --help — display usage message and exit. she's helpful like that 🙈

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🍓 PCP ENVIRONMENT 🍓

environment variables with the prefix PCP_ are used to parameterize the file and directory names that PCP uses. on each installation, the file /etc/pcp.conf contains the local values for these variables 🎀

the $PCP_CONF variable may be used to specify an alternative configuration file, as described in pcp.conf(5) 📖

for environment variables affecting PCP tools, see pmGetOptions(3) — that's the one you want, fr fr 💜

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🌸 SEE ALSO 🌸

PCPIntro(1), pcp(1), pmdadm(1), dmsetup(1) and lvmcache(7). go read them, they slay too ⭐

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okay that's the whole page, bestie!! 💖 this was brought to you by Performance Co-Pilot — the PCP girlies — and it's the PCP-DMCACHE(1) era, periodt 👑🦋 no date stamp on this one but you know the vibe, mwah 💋