RCStor

RCStor is a distributed object storage system designed to utilize regenerating codes.

Installation

We need to switch to the root user. On Ubuntu, run sudo su.

Install golang-1.14:

wget https://dl.google.com/go/go1.14.10.linux-amd64.tar.gz
tar -xvf go1.14.10.linux-amd64.tar.gz -C /usr/local/

Set environmental variable:

echo 'export GOROOT=/usr/local/go' >> ~/.profile
echo 'export GOPATH=$HOME/go' >> ~/.profile
echo 'export PATH=$GOPATH/bin:$GOROOT/bin:/usr/local/bin:$PATH' >> ~/.profile
source ~/.profile

Install rcstor:

git clone https://github.com/rcstor/rcstor.git
cd rcstor
make install

We only need to install rcstor on one server. All binaries will be distributed to other machines through ssh automatically.

Configure SSH

We need to start SSH services on every machine and copy the key of each server to every other servers.

apt update
apt install openssh-client openssh-server
systemctl start sshd
ssh-keygen
ssh-copy-id root@<IP of all machines>

We need to run the above commands on all servers.

Start Directory Service

Run the following command to start directory service.

rcdir start

Configure Volume File

We need to create a json file to specify all the parameters needed to create a volume:

• The IPs of all servers
• The paths of all disks
• Layout (e.g. Geometric, Stripe)
• Layout parameter
• Disk type (i.e. HDD or SSD)
• The exposed port of HTTP server.

Refer to Geo-1M.json and Con-1M.json as the example for volume json file.

Create And Start The Volume

Run the following command on directory server to create and start the volume.

rccli create <JsonFileName>
rccli start <VolumeName>

Run rccli list to check the status of the volume.

Put/Get an object

We can put/get an object from any server. We need to specify an unused object id to put the object into rcstor.

PUT: wget --post-file=<filename> http://<ServerIP>:<HTTPPort>/put/<objectID>

GET: wget http://<ServerIP>:<HTTPPort>/get/<objectID>

Test Degraded Read Time of an Object

We need to run rccli genParity <VolumeName> to generate the parity before testing degraded read. We can find the running result in /usr/local/var/log/rcdir.log. We can proceed only after we find that the operation has completed from the log. Then, we can run the following command to test the degraded time to read an object, rcstor will assume one disk is broken and repair the object.

DGET: wget http://<ServerIP>:<HTTPPort>/dget/<objectID>

Import Data According to the trace

We need to make sure the volume is clean (no object has been put yet) before importing. Run rccli tracePuts <VolumeName> to generate random data sampled from the trace. This may take very long time and involve writing a very large amount of data. We need to check the log to make sure this operation has been completed before moving foward. Then, we need to run rccli genParity <VolumeName> to generate parity for the imported data.

Test Recovery Time

Run rccli recovery <VolumeName>, rcstor will think one of the disk is broken and begin to recover. Then we can start to see the recovery procedure in the log.

Test Average Degraded Read Time

Run rccli traceDgets <VolumeName>, then we can see the result of degraded read in the log.

Test Degreaded Read Time Under Foreground Requests

Run rccli foregroundTraceGets <VolumeName> to start foreground requests, then we run rccli traceDgets <VolumeName> to test degraded read time. We can stop the volume by running rccli stop <VolumeName> afterwards.

Drop the Volume

Run rccli drop <VolumeName>, then we can delete the data for that volume.

Performance Tuning

We can use huge pages to improve the performance of rcstor. Run echo 1000 > /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages