Espresso

Espresso: Constructing Cost-Efficient CXL JBOF via Inter-SSD Computing Resource Sharing!

Introduction

Espresso is a cost-efficient JBOF design that provisions only moderate computing resources per SSD at low monetary cost, while delivering demanded I/O performance through efficient inter-SSD resource sharing. This repository contains the simulator implementation of Espresso, which use SimpleSSD, a popular full-stack to evaluate SSDs and host while employing Xerxes to model the features of CXL.

Please consider citing our paper at OSDI 2026 if you use Espresso. The BibTex is shown below:

TODO

Setup

1. Clone Espresso from github

git clone git@github.com:ChaseLab-PKU/Espresso.git
cd Espresso

2. Build Espresso

cmake -DDEBUG_BUILD=on ..
make -j$(nproc)

If you wish to build Espresso without debug mode, replace ‘on’ with ‘off’ in the ‘cmake’ command line:

cmake -DDEBUG_BUILD=off ..
make -j$(nproc)

Usage

simplessd-standalone <Number of instance (N)> <Output directory> <Simulation configuration file of host>{<Simulation configuration file of instance i> <SimpleSSD configuration file of instance i>} * N

• N: number of SSD instances to simulate
• Output directory: directory for logs and Espresso statistics
• Simulation configuration file of host: host configuration
• Simulation configuration file of instance i: IGL/BIL/SIL configuration
• SimpleSSD configuration file of instance i: SimpleSSD layer configuration

Note: SimpleSSD is a single-threaded simulator. Simulating multiple SSDs can take a very long time, so please be patient. I recommend running multiple simulations in parallel with different configurations.

Example

The config/example/ directory provides a minimal two-SSD, one-to-one compute resource borrowing setup:

File	Description
host.cfg	Host configuration
ssd_hw.cfg	Shared hardware config for both SSDs
ssd0_sw.cfg	SSD 0 (borrower): random writes with a fixed total I/O size, io_size = 256M, iodepth = 128
ssd1_sw.cfg	SSD 1 (lender): almost no I/O, io_size = 0, kept idle to lend resources

Run

mkdir -p output/example_1to1

./simplessd-standalone 2 output/example_1to1 \
  config/example/host.cfg \
  config/example/ssd0_sw.cfg config/example/ssd_hw.cfg \
  config/example/ssd1_sw.cfg config/example/ssd_hw.cfg

When the simulation finishes, the terminal prints per-SSD I/O statistics; Espresso logs are written to the output directory.

Verifying Resource Borrowing and Lending

Inspect espresso_resource*.txt in the output directory:

grep -E 'borrow|lend' output/example_1to1/espresso_resource*.txt

You should see output similar to (ticks vary between runs):

output/example_1to1/espresso_resource0.txt:tick 500894072: SSD 0 set borrow from SSD 1