Hi,

We recently decided to try out glusterfs out in lab as a lot of our processing 
is IOPS bound and our data sets are fairly large (The files that we process on 
are broken up in 256 GB chunks).  Our traditional storage is a 24 disk raid-6 
Synology NAS with SSD cache.  The NAS has a dual 10GbE card connected to 8 
computers in our lab which also have dual 10GbE operating in 802.3ad LACP.  The 
8 processing nodes each have a 1 TB NVME SSD and four of the nodes have a 2 TB 
SATA SSD.  

For testing, I tried creating a distributed replicated volume, and a 
distributed volume.  I also experimented with sharding enabled and tested 
different shard sizes.  For purposes of testing, I created bricks on the 8 NVME 
SSDs using the root partition which is formatted as ext4.  I know this is 
considered bad practice but I could not find documentation on what could go 
wrong (will create dedicated XFS partitions if we decide to migrate to 
glusterfs).  The four 2 TB SATA SSDs are formatted with XFS.  We are using 
Ubuntu 16.04 with GlusterFS 3.8.7.  

When transferring a data chunk from the Synology NAS to a single NVME SSD, we 
get a sustained sequential transfer rate of around 1.0 GB/sec.  When testing 
with GlusterFS, I have not been able to get a write performance greater than 
180MB/sec.  The  throughput is about the same whether I am using a distributed 
volume (1 copy) or a distributed replica 2 volume (twice the network 
bandwidth).  I hit the same performance ceiling copying from the NAS, or 
copying from the NVME SSD to the Gluster volume.  I haven’t done too much 
testing once the data makes it to the Gluster volume as the current throughput 
to upload data to GlusterFS would make it a no go for us.

Does anyone have any ideas on what may be my bottleneck?  Or tips on 
identifying the bottleneck and resolving?

Thanks,
Zack
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