Elliswilson: Created page with "== Overview == OST pools group a subset of OSTs under a named label, allowing administrators to control file placement. Pools are used at file creation time — once a file is created, changing pool membership does not move existing data. Rules: * An OST can belong to multiple pools. * No ordering of OSTs within a pool is defined. * Stripe allocation within a pool follows normal stripe allocation rules. * Pool membership can change at any time; existing files are unaff..."

2026-08-31T15:25:46Z

Created page with "== Overview == OST pools group a subset of OSTs under a named label, allowing administrators to control file placement. Pools are used at file creation time — once a file is created, changing pool membership does not move existing data. Rules: * An OST can belong to multiple pools. * No ordering of OSTs within a pool is defined. * Stripe allocation within a pool follows normal stripe allocation rules. * Pool membership can change at any time; existing files are unaff..."

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== Overview ==

OST pools group a subset of OSTs under a named label, allowing administrators to control file placement. Pools are used at file creation time — once a file is created, changing pool membership does not move existing data.

Rules:
* An OST can belong to multiple pools.
* No ordering of OSTs within a pool is defined.
* Stripe allocation within a pool follows normal stripe allocation rules.
* Pool membership can change at any time; existing files are unaffected.

== Creating and Managing Pools ==

=== Create a Pool ===

<pre>
lctl pool_new fsname.poolname
</pre>

Example:

<pre>
lctl pool_new testfs.flash_pool
</pre>

=== Add OSTs to a Pool ===

<pre>
# Add individual OSTs
lctl pool_add testfs.flash_pool OST[0-3]

# Add a range of OSTs
lctl pool_add testfs.flash_pool OST[0000-0007]

# Add a single OST
lctl pool_add testfs.flash_pool OST0010
</pre>

=== Remove OSTs from a Pool ===

<pre>
lctl pool_remove testfs.flash_pool OST0003
lctl pool_del testfs.flash_pool OST[0004-0007]
</pre>

Note: <code>pool_remove</code> and <code>pool_del</code> are equivalent for removing OSTs from a pool.

=== Destroy a Pool ===

<pre>
# Remove all OSTs first, then destroy
lctl pool_destroy testfs.flash_pool
</pre>

The pool must be empty (all OSTs removed) before it can be destroyed.

== Listing Pools and Pool Membership ==

<pre>
# List all pools in a filesystem
lctl pool_list testfs
lfs pool_list testfs

# List OSTs in a specific pool
lctl pool_list testfs.flash_pool
lfs pool_list testfs.flash_pool

# Also visible via proc
lctl get_param lov.testfs-*.pools.flash_pool
</pre>

== Using Pools for File Striping ==

=== Set a Directory to Use a Pool ===

<pre>
# New files in /mnt/testfs/fast will be striped across flash_pool OSTs
lfs setstripe -p flash_pool /mnt/testfs/fast

# Combine pool with stripe count
lfs setstripe -p flash_pool -c 4 /mnt/testfs/fast
</pre>

=== Create a Single File in a Pool ===

<pre>
lfs setstripe -p flash_pool /mnt/testfs/myfile
</pre>

=== Check Pool Assignment ===

<pre>
lfs getstripe -p /mnt/testfs/fast
lfs getstripe /mnt/testfs/myfile
</pre>

== Pool Quotas ==

Since Lustre 2.14, quotas can be set per OST pool, limiting how much space a user/group/project can consume on a specific pool.

'''Important:''' A global quota limit must be set before pool quota limits will work.

<pre>
# Step 1: Set a global limit (required)
lfs setquota -u alice -B 100T /mnt/testfs

# Step 2: Set a pool-specific limit
lfs setquota -u alice --pool flash_pool -B 1T /mnt/testfs

# View pool quota
lfs quota -u alice --pool flash_pool /mnt/testfs
</pre>

Pool quotas also work with group (<code>-g</code>) and project (<code>-p</code>) quotas.

See [[OST Pool Quotas]] for full details.

== Use Cases ==

=== Tiered Storage ===

Group fast NVMe OSTs into a <code>flash_pool</code> and slower HDD OSTs into an <code>archive_pool</code>. Direct hot data to the flash pool and cold data to the archive pool:

<pre>
lctl pool_new testfs.flash_pool
lctl pool_add testfs.flash_pool OST[0000-0003] # NVMe OSTs

lctl pool_new testfs.archive_pool
lctl pool_add testfs.archive_pool OST[0004-0015] # HDD OSTs

lfs setstripe -p flash_pool /mnt/testfs/scratch
lfs setstripe -p archive_pool /mnt/testfs/archive
</pre>

=== Rack-Aware Placement ===

Group OSTs by physical rack to keep a job's I/O local:

<pre>
lctl pool_new testfs.rack1
lctl pool_add testfs.rack1 OST[0000-0007]

lctl pool_new testfs.rack2
lctl pool_add testfs.rack2 OST[0008-0015]
</pre>

=== FLR Fault Domains ===

With File Level Redundancy (FLR/mirroring), place each mirror on a different pool to ensure hardware fault isolation:

<pre>
lfs mirror create -N -p pool_a -N -p pool_b /mnt/testfs/critical_file
</pre>

== See Also ==

* [[Lustre Striping Best Practices]]
* [[Creating and Managing OST Pools]]
* [[OST Pool Quotas]]

[[Category:Lustre Systems Administration]]
[[Category:Lustre Storage Management]]

Lustre OST Pool Management - Revision history