LLSOM_SYNC(8)

💖 llsom_sync(8) — the Lustre Configuration Utilities glow-up 💖

okay bestie, buckle up, because we're learning llsom_sync(8) and honestly? it's giving "quietly essential". let's go 🦋

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✨ NAME ✨

llsom_sync — a lil utility that syncs the file LSOM xattr. that's it, that's the whole job description 💅

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🎀 SYNOPSIS 🎀

llsom_sync {--mdt|-m}=MDT {--user|-u}=USER_ID [--daemonize|-d]
           [--verbose|-v] [--interval|-i] [--min-age|-a] [--max-
           cache|-c] [--sync|-s] LUSTRE_MOUNT_POINT

note the -m and -u are mandatory, no cap, the rest are optional besties ✨

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🌸 DESCRIPTION 🌸

so llsom_sync is designed to sync the file LSOM xattr in the Lustre Filesystem, and it does this by using Lustre MDT changelogs. iconic behavior.

⚠️ real talk though: a changelog user must be registered (peep lctl(8) changelog_register) before you use this tool. no registration, no vibes, no sync. periodt.

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💅 OPTIONS 💅

• -m, --mdt=MDT — the metadata device whose files need their LSOM xattr synced. heads up: a changelog user must be registered for this device 🫶
• -u, --user=USER_ID — the changelog user id for that MDT device up above. see lctl(8) changelog_register for the deets 👑
• --daemonize — makes the program daemonize. in daemon mode, the utility will scan, process the changelog records, and sync the LSOM xattr for files periodically, like a lil robot doing cardio 🏃♀️
• --verbose — produce a verbose output. yap mode: ON 📢
• --interval — the time interval to scan the Lustre changelog and process the log record, in daemon mode ⏰
• --min-age — the time that llsom_sync tool will not try to sync the SOM data for any files closed less than this many seconds old. the default min-age value is 600s (10 minutes). so if it's fresher than 10 min, she's not touching it 🙈
• --max-cache — the total memory used for the FID cache, and it can be with a suffix [KkGgMm]. the default max-cache value is 256MB. and here's the cute lil twist: for the parameter value < 100, it is taken as the percentage of total memory size used for the FID cache instead of the cache size. so 50 ≠ 50 bytes, bestie, it means 50% 🔥
• --sync — sync file data to make the dirty data out of cache, to ensure the blocks count is correct when updating the file LSOM xattr.

😭 okay so about --sync: this option could hurt server performance significantly if thousands of fsync requests are sent. she's powerful but she's a lot. use with intention, not on a whim 💀

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🌈 EXAMPLES 🌈

register a changelog consumer for MDT lustre-MDT0000:

# cl_user=$(ssh root@mds01 lctl --device lustre-MDT0000 changelog_register -n)
# echo $cl_user
cl1

after performing some file operations on the Lustre Filesystem with mount point /mnt/lustre and the filesystem undergoing some changes, sync file LSOM xattr:

# llsom_sync --mdt=lustre-MDT0000 --user=$cl_user --verbose /mnt/lustre

to deregister the changelog user (e.g. after this example, or if SOM updates are no longer needed):

# ssh root@mds01 lctl --device lustre-MDT0000 changelog_deregister $cl_user

like, clean up after yourself?? we love a responsible queen 🧚

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⭐ AVAILABILITY ⭐

the llsom_sync command is part of the lustre(7) filesystem package since release 2.12.0. so she's been around, she's established, she's that girl 💜

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🦋 SEE ALSO 🦋

lustre(7), lctl(8)

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and that's the whole page, bestie!! 🎀 this one comes to you from Lustre, dated 2024-08-28, and yeah the footer says LLSOM_SYNC(8) because obviously. now go register that changelog user before you run anything, i'm serious 😭💖