DS1817+ Poort Performance

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DS1817+ Poort Performance

Postby Randvegeta » Tue Nov 21, 2017 4:44 pm

Hello all.

Couple of weeks ago I purchased 2x DS1817+ with the optional dual 10G SPF+ cards.

I'm looking to deploy these as a high availability storage cluster for a small Xen HA virtualization cluster.

One of the DS1817+ units (Call it NAS A)is configured as so:

6x4TB HDD (RAID 10, ext4)
2x480GB SSD (RAID 1 SSD Caching for 10TB RAID 10 volume)

The second DS1817+ (call it NAS B)has 6x3TB HDD in RAID 6, which has the same amount of usable disk space as the RAID 10 array. No SSD caching.

NAS A and B are directly connected to each other via the 2nd 10G port. They both connect to a 10G switch of which the Xen nodes are also connected.

The idea is to use NAS A as the 'primary' storage and NAS B as the backup, in case NAS A fails in some way. NAS A and B are supposed to be configured in SHA mode.

I have yet to actually put the Synology NASs into high availability clustering yet as I am still testing the performance and I am getting some very strange, and generally quite poor results.

Basic tests directly on NAS A (connected through SSH) shows I can write to the RAID 10 array at about 200-400MB/s. The performance is very uneven and the performance does not improve with SSD caching activated. I have created an ISCSI LUN and connected it to a Xen node where I created a VM where the virtual disk is hosted on on the NAS. Performance varied from 50-110MB/s. Which is worse than local disk, and less than 1/4 the speed I am seeing directly on the NAS itself.

I decided to test NAS B, which is in RAID 6. Other than the RAID type, they are configured in the same way. So I created the same kind of iSCSI LUN, same size and same settings. Then created a VM on the same node. This time, the write speed of the VM to the virtual disk is about 350MB/s. 3-7x faster than the RAID 10 version.

Why on earth would the RAID 6 perform better than the RAID 10 array on the same NAS model? Connected to the same switch, running VMs on the same node.

I was expecting speeds of about 400-600MB/s on the RAID 10 array, and considerably less performance on the RAID 6.

Any idea what's going on?

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