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Raid 5 terrible performance with Thunderbay 4

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(@softraid-support)
Posts: 8008
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This was from running in expired trial mode, in working with the user.

 
Posted : 31/01/2017 6:28 pm
(@softraid-support)
Posts: 8008
Member Admin
 

Hi, I recently purchased a thunderbay 4 and getting terrible performance. My write speeds in Raid 5, or Raid 4 is only 100-120 MB no matter what I try.

To clarify this thread:
If the write cache for a RAID 4/5/10 volume is disabled, write performance will be much slower. There are two ways for write cache to be disabled:
A) Expired Trial mode disables the write cache.
B) Disabling Write Cache in the SoftRAID RAID preferences

Write Cache is important for write performance in RAID 4/5, as parity must be calculated in real time, and without caching this data into reserved RAM (until it can be written out to disk), performance will be poor on RAID 4/5 volumes.

The reason to intentionally disable Write Cache is to make your volume more reliable, especially if you are subject to power outages (get a UPS), brownouts (get a power conditioner, always a recommended option to make your computers/gear last longer), or if your computer is crashing for inexplicable reasons. When your computer crashes, data sent to the disks, but not yet written out, can cause corruption in the file directory. Disabling the Write Cache on RAID volumes minimizes this problem, as all data is written directly to disk, rather than cached until the disks are less busy. However, this has an impact on write performance.

Other than disabled Write Cache, there is no reason for RAID performance numbers not to match our published figures.

If your performance differs significantly, first ensure your volume has no data. Otherwise you are performing an invalid comparison, especially if your volume is full, or if data on the volumes is fragmented (scattered around the volume).

Other reasons are perhaps there is a hardware problem, or your drives/subsystems are significantly slower than what we used in our testing. (we generally use standard, off-the-shelf Thunderbay 4 enclosures from OWC, with standard Toshiba or Hitachi disk drives.) We do not use "customized" configurations to improve our numbers, any one should be able to achieve these with their standard hardware.

USB will always be much slower than Thunderbolt enclosures, USB is not really suited for high performance RAID application.

Note also that a Mac Pro will provide slightly better numbers than slower computers, or computers with less cores.

Hope this information clarifies this subject.

Feel free to keep discussing!

 
Posted : 01/02/2017 2:42 pm
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