Velocity solo duo x2 Raid 0 SSD read speed decreases

RomerosDaniel

macrumors newbie
Original poster
Oct 5, 2016
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Please help! This is frustrating and disappointing :( (CORRECTION: Thread title; I meant WRITE speed, not read speed)

I have recently added a second 1TB 850 EVO (so, 2 1TB 850's) running on the Velocity solo duo card (connected on the 2nd pcie slot) and running RAID 0 stripped (64k block size) on Yosemite. A major issue I'm experiencing on the BlackMagic test, is that the write speed starts at near 500mb/s, but then gradually declines to about 97mb/s :confused: after a few passes (meaning it drops to 97mb/s before starting the read speed test). Why would this be happening? The read speed is fine, which stay at a consistent near 700mb/s.

I had been using one of the 850's on the Duo before I got another one, and the r&w speeds were consistent (450-490mb/s), with no problems. But now that I have added a second 850, I get a HUGE decline in write speed :eek:. Whyyyyy???

I wiped both drives in disk utility before creating the RAID 0, and I Time Machine restored from my external HDD after the RAID was created (using the RAID as boot drive).

Any suggestions?? Your help is much appreciated!

My specs:

2008 early Mac Pro
Yosemite 10.10.5
2 x 2.8 GHz Quad-Core Intel Xeon
32 GB 800MHz DDR2
ATI Radeon HD 4870 1GB
 
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h9826790

macrumors G5
Apr 3, 2014
12,768
5,579
Hong Kong
In fact, if you didn't test your SSD just before setup RAID 0. And you never enable TRIM by yourself. Then I suspect your write performance is actually already low before you setup RAID 0.

When the SSD is new, there are lots of empty cell. So, the write performance is good. Without TRIM, your SSD's write performance will not be able to maintain when running out of empty cell (even thought there are lots of "empty space" in your file system).

So, if you only benchmarked your SSD when it was new. And you never ever activate TRIM. I suspect you have this slow write problem long before you setup the RAID 0 array.

For 10.10.5, you can simply enable TRIM by running a terminal command

Code:
sudo trimforce enable
After you run this command, and reboot.

Leave the computer idle for may be 30min. And then run the test again. However, I am not 100% sure if software RAID can utilise TRIM. But at least it won't hurt anything and worth to try.
 

m4v3r1ck

macrumors 68020
Nov 2, 2011
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The Netherlands
Yes, my 840 EVO 1TB Apple SOFTraid0 (2x 500GB) scratch disk and my two OS (OS X & Windows 10) SSD's are all being trimmed. I'm still getting very satisfying read/write performance on the DUO x2. My two OS drives and RAID0 scratch are still going strong since my purchase in 10/2013.




Keep us posted about the outcome of the trim and your 'new' performance!

Cheers
 
Last edited:

m4v3r1ck

macrumors 68020
Nov 2, 2011
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It's indeed a bit confusing. Reading on i.e. Apple (Support) website, many threads/KB's mention the Apple Software RAID utility. My screen-cap also say Apple_RAID, so that must be the correct name for it.

I also have an Apple_RAID0 on 2x 2GB HDD's connected to the internal bays. Never ever had any issues with the Apple_RAID's, I've always found them very stable in use.

(I'm working with the Apple (Software) RAID since I ditched the Apple Raid Card, which I bought with my Mac Pro 3.1 in 2008. A horrible 'Pro' product that caused many, many issues and data loss.)

Cheers
 

RomerosDaniel

macrumors newbie
Original poster
Oct 5, 2016
9
4
In fact, if you didn't test your SSD just before setup RAID 0. And you never enable TRIM by yourself. Then I suspect your write performance is actually already low before you setup RAID 0.

When the SSD is new, there are lots of empty cell. So, the write performance is good. Without TRIM, your SSD's write performance will not be able to maintain when running out of empty cell (even thought there are lots of "empty space" in your file system).

So, if you only benchmarked your SSD when it was new. And you never ever activate TRIM. I suspect you have this slow write problem long before you setup the RAID 0 array.

For 10.10.5, you can simply enable TRIM by running a terminal command

Code:
sudo trimforce enable
After you run this command, and reboot.

Leave the computer idle for may be 30min. And then run the test again. However, I am not 100% sure if software RAID can utilise TRIM. But at least it won't hurt anything and worth to try.
So, you're saying run this "sudo trimforce enable" after the RAID 0 is setup and I'm fully Time Machine restored? Or do I run the command before creating the RAID 0 (like in disk utility in restore mode)?

EDIT: is there also anyway to see if TRIM is infact enabled? I feel the first 850 I have been using may have TRIM enabled, where as the new one I just added, doesn't.

EDIT (again): ok I found this article that tells people how to do the command and how to see if TRIM is enabled. I just looked, and both my 850's say, "TRIM Support: No". I'm assuming because I wiped them both. Is that true, that if you wipe (erase) the drive through disk utility, that TRIM will be defaulted to off?

I'm going to redo the RAID 0, and then run the "sudo trimforce enable" command, and I'll get back to you guys to see if performance enhances!

Yes, my 840 EVO 1TB Apple SOFTraid0 (2x 500GB) scratch disk and my two OS (OS X & Windows 10) SSD's are all being trimmed. I'm still getting very satisfying read/write performance on the DUO x2. My two OS drives and RAID0 scratch are still going strong since my purchase in 10/2013.




Keep us posted about the outcome of the trim and your 'new' performance!

Cheers
Did you use the "sudo trimforce enable" command that h9826790 suggested I do?

Also, what settings did you do for your RAID 0 setup? (Block size, stripped, anything else?)
 
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m4v3r1ck

macrumors 68020
Nov 2, 2011
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The Netherlands
Did you use the "sudo trimforce enable" command that h9826790 suggested I do?

Also, what settings did you do for your RAID 0 setup? (Block size, stripped, anything else?)
1. Yes, [edit:] BEFORE creating the RAID0 I entered the "sudo trimforce enable" command in Terminal for system wide trim enabled for all SSD's.

2a. Settings in DU for my AppleRAID0:


2b. As I'm processing video's I choose:



Looking forward to your feedback after creating AppleRAID0 and using the "sudo trimforce enable" command in Terminal. To check the trim enabled in your About This Mac (see my first screen-cap in post#5).

Cheers
 
Last edited:

RomerosDaniel

macrumors newbie
Original poster
Oct 5, 2016
9
4
1. Yes, after creating the RAID0 I entered the "sudo trimforce enable" command in Terminal

2a. Settings in DU for my AppleRAID0:


2b. As I'm processing video's I choose:



Looking forward to your feedback after creating AppleRAID0 and using the "sudo trimforce enable" command in Terminal. To check the trim enabled in your About This Mac (see my first screen-cap in post#5).

Cheers
Awesome! Thank you for detailed info!

I will surely get back to you all and see if the performance gets better! (currently restoring from Time Machine again since I deleted the RAID to test both drives individually. Both seem to be fine individually, so I redid the RAID 0 and now restoring in TM...will take few hours)
 
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RomerosDaniel

macrumors newbie
Original poster
Oct 5, 2016
9
4

Wooo! Works like charm now :)

Thank you guys for your help, I really appreciate it!

Yes, my 840 EVO 1TB Apple SOFTraid0 (2x 500GB) scratch disk and my two OS (OS X & Windows 10) SSD's are all being trimmed. I'm still getting very satisfying read/write performance on the DUO x2. My two OS drives and RAID0 scratch are still going strong since my purchase in 10/2013.




Keep us posted about the outcome of the trim and your 'new' performance!

Cheers
M4v3r1ck, is there anything special you done (software/hardware) that gave you 708MB/s? Our Reads are about the same, but you have 108MB/s writes more than I have, and I'm using 2 1TB Evo 850's, while you're using 2 500GB 840's. Is there really that much of difference between the drives we have or could it be that your block size is at 256k, while mine is at 64k?

Thanks again for your help! :D
 

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m4v3r1ck

macrumors 68020
Nov 2, 2011
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Your welcome! Glad to be of help. As for the blocksize I used the 'recommended' largest of 256K for large video files.

As I need to update my 840 EVO 500 GB (in RAID0) SSD firmware tomorrow, I'll delete the RAID0 and shall perform some tests with all the different blocksizes that can be used. Will report back here, this time with the AJA Disk Bench Tool. Practicing / having fun at the same time.

After that I'll restore my backup to the RAID0.

Cheers
 

m4v3r1ck

macrumors 68020
Nov 2, 2011
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For comparison I created a AppleRAID0 with block size 64KB:




While SoftRAID (v5.5) recommends 128 KB for editing large video files on RAID0 scratch disks:



Well, let's not focus on the benches I showed. More important is that your write speeds @64KB AppleRAID0 are not according the specs and for sure not ~equal your read speeds. You did use BM with a 4GB stress?

Cheers
 

RomerosDaniel

macrumors newbie
Original poster
Oct 5, 2016
9
4
For comparison I created a AppleRAID0 with block size 64KB:




While SoftRAID (v5.5) recommends 128 KB for editing large video files on RAID0 scratch disks:



Well, let's not focus on the benches I showed. More important is that your write speeds @64KB AppleRAID0 are not according the specs and for sure not ~equal your read speeds. You did use BM with a 4GB stress?

Cheers

I used BM 5GB and 4GB stress test, and get the same results (596mb/s write and 687 mb/s read):confused:, and this is with 64k Block size. Are you saying there is something wrong with my drives (RAID 0) since the read/write speeds are not close to similar?


Omg, I just realized that one of my SSD's are an 840 and the other is 850 :eek: Could this be why I am getting lesser speeds than your RAID 0 configuration, because the two SSD's are different?
 

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m4v3r1ck

macrumors 68020
Nov 2, 2011
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A mistake easily made ;) so no problem.
I don't have the knowledge to tell for 100% sure that a different model will cause this issue cause I have allways used exact same drives using in RAIDS but seeing your bench I would.

Cheers