diff --git a/deploy/compose.yaml b/deploy/compose.yaml
index a14c569..e4ba38a 100644
--- a/deploy/compose.yaml
+++ b/deploy/compose.yaml
@@ -132,6 +132,10 @@ services:
     command:
       - mini
       - -dir=/data
+      # A bucket is a SeaweedFS collection and claims a block of volumes. The ~1 GB automatic
+      # volume size leaves modest hosts with room for only a few collections; after that, writes
+      # stall instead of failing. This changes allocation granularity, not object or total capacity.
+      - -master.volumeSizeLimitMB=32
       - -s3.port.https=8443
       - -s3.cert.file=/run/ekklesia/tls/object-storage.crt
       - -s3.key.file=/run/ekklesia/tls/object-storage.key
diff --git a/tests/deploy.test.ts b/tests/deploy.test.ts
index 461a4c3..64ed045 100644
--- a/tests/deploy.test.ts
+++ b/tests/deploy.test.ts
@@ -138,7 +138,7 @@ describe("reference deployment compose files", () => {
       ]),
     );
     expect(services["object-storage"]?.command).toEqual(
-      expect.arrayContaining(["-s3.port.https=8443"]),
+      expect.arrayContaining(["-master.volumeSizeLimitMB=32", "-s3.port.https=8443"]),
     );
 
     const hba = (await text("postgres/pg_hba.conf"))