diff --git a/repos/dde_rump/lib/mk/rump_common.inc b/repos/dde_rump/lib/mk/rump_common.inc
index ce4aa7dfbb..dc02245539 100644
--- a/repos/dde_rump/lib/mk/rump_common.inc
+++ b/repos/dde_rump/lib/mk/rump_common.inc
@@ -1,7 +1,7 @@
 RUMP_PORT_DIR := $(call select_from_ports,dde_rump)/src/lib/dde_rump
 RUMP_BASE     := $(BUILD_BASE_DIR)/var/libcache/rump
 
-CC_C_OPT += -D__NetBSD__ -D'CTASSERT(x)=' -DMAXPHYS=32768 -D_RUMP_NATIVE_ABI \
+CC_C_OPT += -D__NetBSD__ -D'CTASSERT(x)=' -DMAXPHYS=1048576 -D_RUMP_NATIVE_ABI \
             -DMAXUSERS=32 -DCOMPAT_50=1 -DCOMPAT_60=1 -DDIAGNOSTIC -DKTRACE \
             -DRUMP_KERNEL_IS_LIBC -D_RUMPKERNEL -D_KERNEL -DMULTIPROCESSOR \
             -D_MODULE -DMODULAR -DRUMP_USE_CTOR
diff --git a/repos/dde_rump/run/libc_vfs_ext2.run b/repos/dde_rump/run/libc_vfs_ext2.run
index 653ea3d72c..12b02f39e1 100644
--- a/repos/dde_rump/run/libc_vfs_ext2.run
+++ b/repos/dde_rump/run/libc_vfs_ext2.run
@@ -3,7 +3,7 @@ set mkfs_opts "-F"
 
 set test_build_components "lib/vfs_rump"
 
-set test_vfs_config "<rump fs=\"ext2fs\" ram=\"7M\" writeable=\"yes\"/>"
+set test_vfs_config "<rump fs=\"ext2fs\" ram=\"10M\" writeable=\"yes\"/>"
 
 set test_boot_modules {
 	rump_fs.lib.so
diff --git a/repos/dde_rump/run/libc_vfs_fs_ext2.run b/repos/dde_rump/run/libc_vfs_fs_ext2.run
index 205435e502..653d6e740c 100644
--- a/repos/dde_rump/run/libc_vfs_fs_ext2.run
+++ b/repos/dde_rump/run/libc_vfs_fs_ext2.run
@@ -8,7 +8,7 @@ set mkfs_opts "-F"
 
 set test_build_components "lib/vfs_rump"
 
-set test_vfs_config "<rump fs=\"ext2fs\" ram=\"7M\" writeable=\"yes\"/>"
+set test_vfs_config "<rump fs=\"ext2fs\" ram=\"10M\" writeable=\"yes\"/>"
 
 set test_boot_modules {
 	rump_fs.lib.so
diff --git a/repos/dde_rump/run/rump_ext2.run b/repos/dde_rump/run/rump_ext2.run
index 592c7e137a..00697e0dfa 100644
--- a/repos/dde_rump/run/rump_ext2.run
+++ b/repos/dde_rump/run/rump_ext2.run
@@ -39,7 +39,7 @@ create_boot_directory
 # Generate config
 #
 append config {
-<config>
+<config verbose="yes">
 	<parent-provides>
 		<service name="ROM"/>
 		<service name="IRQ"/>
@@ -73,7 +73,7 @@ append config {
 		</config>
 	</start>
 	<start name="vfs" caps="200">
-		<resource name="RAM" quantum="16M" />
+		<resource name="RAM" quantum="25M" />
 		<provides><service name="File_system"/></provides>
 		<config>
 			<vfs> <rump fs="ext2fs" ram="10M"/> </vfs>
diff --git a/repos/dde_rump/src/include/util/allocator_fap.h b/repos/dde_rump/src/include/util/allocator_fap.h
index 2481470b82..499de98a28 100644
--- a/repos/dde_rump/src/include/util/allocator_fap.h
+++ b/repos/dde_rump/src/include/util/allocator_fap.h
@@ -56,7 +56,7 @@ namespace Allocator {
 		private:
 
 			enum {
-				BLOCK_SIZE = 2 * 1024  * 1024,     /* 2 MB */
+				BLOCK_SIZE = 4 * 1024  * 1024,     /* bytes */
 				ELEMENTS   = VM_SIZE / BLOCK_SIZE, /* MAX number of dataspaces in VM */
 			};
 
diff --git a/repos/dde_rump/src/lib/rump/io.cc b/repos/dde_rump/src/lib/rump/io.cc
index 67b95f1e1f..f710df4f5b 100644
--- a/repos/dde_rump/src/lib/rump/io.cc
+++ b/repos/dde_rump/src/lib/rump/io.cc
@@ -107,7 +107,15 @@ class Backend
 
 		Genode::Allocator_avl  _alloc   { &Rump::env().heap() };
 		Genode::Entrypoint    &_ep      {  Rump::env().env().ep() };
-		Block::Connection<Job> _session {  Rump::env().env(), &_alloc };
+
+		/*
+		 * The tx_buf_size is chosen such that one I/O request fits into the
+		 * I/O buffer at once. The size of NetBSD's I/O requests is bounded by
+		 * the definition of MAXPHYS. The 64 KiB are added to account for the
+		 * space needed for the submit/ack queues.
+		 */
+		Block::Connection<Job> _session {  Rump::env().env(), &_alloc,
+		                                   1024*1024 + 64*1024 };
 		Block::Session::Info   _info    { _session.info() };
 		Genode::Mutex          _session_mutex;
 		Io_signal_blockade     _io_signal_blockade { _ep,
diff --git a/repos/libports/run/libc_vfs_filesystem_test.inc b/repos/libports/run/libc_vfs_filesystem_test.inc
index 6c2386a87a..48fab0b55c 100644
--- a/repos/libports/run/libc_vfs_filesystem_test.inc
+++ b/repos/libports/run/libc_vfs_filesystem_test.inc
@@ -68,7 +68,7 @@ set config {
 		<provides> <service name="Timer"/> </provides>
 	</start>
 	<start name="test-libc_vfs" caps="200">
-		<resource name="RAM" quantum="10M"/>
+		<resource name="RAM" quantum="28M"/>
 		<config>
 			<iterations value="1"/>}
 append_if [have_include "power_on/qemu"] config {
@@ -104,7 +104,7 @@ append config {
 
 append_if $use_vfs_server config "
 	<start name=\"vfs\" caps=\"200\">
-		<resource name=\"RAM\" quantum=\"12M\" />
+		<resource name=\"RAM\" quantum=\"24M\" />
 		<provides><service name=\"File_system\"/></provides>
 		<config>
 			<vfs>
diff --git a/repos/ports/run/virtualbox_auto.inc b/repos/ports/run/virtualbox_auto.inc
index ea0884506b..ab50964b12 100644
--- a/repos/ports/run/virtualbox_auto.inc
+++ b/repos/ports/run/virtualbox_auto.inc
@@ -152,11 +152,11 @@ append_if [have_spec nova] config {
 append_if [expr $use_rumpfs] config {
 	<start name="rump_fs" priority="-1" caps="200">
 		<binary name="vfs"/>
-		<resource name="RAM" quantum="32M"/>
+		<resource name="RAM" quantum="64M"/>
 		<provides><service name="File_system"/></provides>
 		<config ld_verbose="yes">
 			<vfs>
-				<rump fs="ext2fs" ram="28M"/>
+				<rump fs="ext2fs" ram="48M"/>
 			</vfs>}
 
 append_if [expr $use_rumpfs && $use_ram_fs && $use_overlay_from_disk] config {