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August 12th, 2025 09:35
Emc Unity 300 Speed Issue
Hello,
I have an Emc Unity 300 controller (12x7.68 SSD 4x16 base + 2 extra 16g I/O modules) and I use 2 16 SAN switches.
A and B controllers are connected to SAN-A and SAN-B with 4 Om4 16 Gb FC cables each. There are 3 hosts, and each host is connected to SAN-A and SAN-B via 16G FC.
When I initiate a simultaneous disk read/write speed test from 2 hosts, the total speed does not exceed 2.4GB/s.
It seems as though the total speed is limited to 16G. I am using ESX8 as the operating system. What could be causing this issue?
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DELL-Sam L
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August 12th, 2025 16:17
Hello Maho1963
There are many reasons that you can be getting that speed. What Is the current OS on your Unity 300 system as you didn’t state that in your post? When you deployed your Unity 300 system do you follow the guides listed below?
https://www.dell.com/support/kbdoc/en-us/000009649
https://dl.dell.com/content/docu69891_best-practices-guide-best-practices-for-performance-and-availability.pdf?language=en-us
Maho1963
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August 13th, 2025 10:49
@DELL-Sam L Unisphere Version 5.4.0.
My friend did the installation, he is experienced in this field.
He told me that no matter how many hosts are connected, the total speed cannot exceed FC 16g.
For example, if we consider that the device can achieve a speed of 10 GB/s with 12 7.68 SSDs (RAID 5), I think that when I connect 4 hosts, I should be able to achieve a read speed of 2.5 GB/s per host.
Is this theoretically correct?
DELL-Sam L
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August 13th, 2025 13:19
Hello Maho1963,
The 16g speed is a max burst speed that the system can handle. As for a sustained speed it is often times lower than the max burst speed. It is not theoretically possible to have 16g all the time to all connections.
Maho1963
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August 13th, 2025 15:09
@DELL-Sam L
Thank you for your reply.
From what I understand, even if there are four servers connected to the storage, the maximum speed I can achieve will not exceed 1.6 Gb/s.
For example:
Server-1: 200 Mb/s
Server-2: 300 Mb/s
Server-3: 1000 Mb/s
Server-4: 100 Mb/s
Total speed: 1.6 Gb/s
DELL-Sam L
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August 13th, 2025 16:22
Hello Maho1963,
In most cases you would be correct. Without knowing the FC card that is in your hosts as well as the type of switch that the host and the storage is connected to I couldn’t say for sure that you can’t get better performance. When we look at performance issues we like to know the whole environment of the data center as it helps to pin point bottle necks that can be leading to potential performance issues.