Raid 5 perfomance d...
 
Notifications
Clear all

Raid 5 perfomance decreasing

(@alecxx)
Active Member Customer

Hi,

I must admit I´m happy with SR so far: I own an OWC Enclosure (TB 4 Raid5 deition) and have 4 Seagate st3000dm0001 in raid 5.

The perfomances ( measured with Black magic and Quick Bench 4.0) with an empty array topped 500MB/S W and R.

After having occupied 2TB, I can´t hardly get over 370MB/S W and R.

I thought it was related to the enclosure, then i had the chance to test my array on a Akitio Quad Tb2 enclosure getting the same results.

Is that a normal behaviour or something is wrong? This is the same speed I get on a LAcie 2 Big Tb1 configured in Apple Raid 0 (same disks inside).

Thank you in advance for advising,
Alex

Quote
Topic starter Posted : 12/04/2016 2:41 am
(@softraid-support)
Member Admin

A benchmark test will give its best results on a new volume. Then there is no fragmentation and the files written by the test are on the fastest parts of the drive.

Once a volume is used, and files are stored all over the volume (from editing/copying/deleting), performance will of course slow down. Benchmarks will exaggerate this effect, as they work best with all clear, contiguous space to write/read to.

ReplyQuote
Posted : 12/04/2016 10:26 am
(@alecxx)
Active Member Customer

A benchmark test will give its best results on a new volume. Then there is no fragmentation and the files written by the test are on the fastest parts of the drive.

Once a volume is used, and files are stored all over the volume (from editing/copying/deleting), performance will of course slow down. Benchmarks will exaggerate this effect, as they work best with all clear, contiguous space to write/read to.

Hi, Thank you for your quick reply.
I´m not sure, but I sense it worsened since I´ve updated to the 5.5.

What do you suggest? Should I format the volume and run a test on a empty drive?

Thank you.

ReplyQuote
Topic starter Posted : 12/04/2016 10:58 am
(@softraid-support)
Member Admin

First of all, the SoftRAID driver is extremely fast with response times in microseconds. There are no scenarios where the SoftRAID driver can cause slowdowns. Hence, all slowdowns are hardware related.

If you are getting a gradual reduction in performance, it could be caused by the volume getting full, or volume fragmentation. (SSD's can gradually lose performance also, but that is a complex subject). It is also possible that problems with the OS installation, file system or third party applications can cause performance issues.

If you get sudden reductions in performance, then it can be caused by a disk (retrying sectors for example), bus resets (bad enclosure or cabling), etc.

A "benchmark" test can only be considered valid for a freshly created or erased volume. Otherwise there are too many variables to expect the results to be consistent and valid.

Performance issues have be be systematically and symptomatically approached. Figure out what is different. Isolate variables. Test by changing one variable at a time to isolate the possible problem. You also need to use consistent settings in your testing. Use real world testing (finder copy for example) rather than rely on a benchmark which may or may not reflect the real world.

370Mb/s is not a bad result for a "used" volume, though.

ReplyQuote
Posted : 12/04/2016 11:40 pm
Share:
close
open