(Scary) RAID 0 performance decrease

There are several reasons why it could slow down.

First is TRIM. Without TRIM, as an SSD fills up, they get slower and slower. If you enable TRIM in the OS, then SoftRAID can support TRIM on the device. (there is a "trimforce enable" command in terminal for 10.10.5 or later).

Second is some of the Samsung devices seem to age badly, in our experience. One example is we have a laptop in the lab with a Samsung SSD in it. Originally it was performance at 300+MB/s speeds. Recently we measured it at only 3MB/s!!! Really, it was that slow. We certified the SSD and performance increased to 120MB/s, but still much slower than expected. We will be replacing it soon. We know that this is "anecdotal" evidence, but we have had a couple other users with similar experiences. It is possible your drives are entering this older age period where performance drops dramatically.

Try a certify disk on your Samsung (this is destructive, so backup all data first!)
Make sure you do a 2 pass or 3 pass certify. Enable TRIM. Then when you set up your volume again, see if performance is acceptable again.

if not, replace the SSDs.

Thank you. Wow! One year old and possibly wearing out....hmmmm might need a different SSD supplier. Will try your suggestions first. They have only ever been 60-75% capacity, now using OSX 10.11 & SR 5.5.5.

Thanks
J

Job done and now we are at R/W of 730/680 which is better, but still lacking greatly from when new. Incidentally tested a current 5K iMac with 500GB factory SSD with R/W of 1480/1860 !!!

Also, I was considering adding another 850 pro 1TB SSD to these existing SSD's to go 3-way scary raid will that provide noticeable improvement? If not are there 'know more resilient' SSD's (1TB) than what I'm using?

Thank you
J

I wonder what Samsung will tell you?
What you should do is individually "verify" disk and watch Activity monitor. See what numbers you are getting, if both are slow, or mostly just one SSD.
You can also do a zero disk to get an idea of write speeds, but that requires backup as this will destroy the volume.
(cancel both operations with command . or using the utilities menu to cancel)

If you get unacceptable numbers with either test, it gives you a claim against Samsung, as neither test is using a driver, it is raw throughput to the device.

Do you have TRIM enabled? It may help keep speeds consistent on these devices. SSD's should show some degradation over time, but your situation is more extreme than most.

Trim done, both drives performing similarly so I guess its degradation. Do you think it would have degraded less had I had trim enabled sooner? Whatever the case I'm not too impressed with the performance of these 850 Pro's over the medium to long term.

Thank you for your assistance, might try a RMA to Samsung...

no, I don't think your drives would be faster if TRIM was on longer.

Interesting to hear what Samsung says.

If anyone else has similar slowdown issues with Samsung SSD's, please post them here!

no, I don't think your drives would be faster if TRIM was on longer.

Interesting to hear what Samsung says.

If anyone else has similar slowdown issues with Samsung SSD's, please post them here!

Well this is an interesting thread that had me sign up to comment.

I have a Mid 2012 MBP 13" that I tweaked years ago a soon as the warranty expired. Regrettably, I performed all my modifications at once and did not measure the performance gains incrementally. It's a 2.5GHz i5 with 16 GB RAM, DVD removed and OWC drive caddy installed to accommodate a pair of 128 GB Samsung 840 Pro SSDs in RAID 0. Initially, the performance was fantastic with read/write speeds of 950/725 using Blackmagic. Boot times were at the 11 second mark when the array way initially installed under Mavericks. I noticed a steady decrease in performance over time and had assumed it was an aging MBP that was starting to struggle with the latest incarnations of OSx.

I recently ran Blackmagic again to demonstrate the speeds to a co-worker and was shocked to see Blackmagic read/write speeds of 110/28!!! Co-worked laughed and told me he had faster micro SD cards!

Trim is and has always been enabled. Seems like a gradual loss in performance and am curious if a certify disk routine will restore its (or some of its) performance. It may just be time to enlarge my array anyhow as I'm approaching 75% usage of the storage capacity. May consider another brand of SSDs considering...