Slow SM951 AHCI Blade?

[dickiedunn]

Hello,

This is my first post. I'm running a MP 5,1, Sierra, booting from a Samsung SM951 (512GB) blade mounted to an Angelbird PX1 card in slot 3. Aja performance test shows 477 MB/Sec Write and 1443 MB/Sec Read. The write speed starts off at around 1000 MB/s and then when 3/4 full (I'm running a 16 GB test), it slows way down at then end. Is this normal behavior for this blade? Do these blades slow down as they fill up? I've got 54.71 GB available.

I've attached a image of the Write speed. I drops suddenly towards the end of the test.

I'd love to add some more flash storage too. I'm not sure if it makes sense to get another NVME drive to use on another PCIe slot, or just to get an SSD to put in one of the drive bays.

Thanks for any insight,

DD

 

[AlexMaximus]

Hello,

This is my first post. I'm running a MP 5,1, Sierra, booting from a Samsung SM951 (512GB) blade mounted to an Angelbird PX1 card in slot 3. Aja performance test shows 477 MB/Sec Write and 1443 MB/Sec Read. The write speed starts off at around 1000 MB/s and then when 3/4 full (I'm running a 16 GB test), it slows way down at then end. Is this normal behavior for this blade? Do these blades slow down as they fill up? I've got 54.71 GB available.

I've attached a image of the Write speed. I drops suddenly towards the end of the test.

I'd love to add some more flash storage too. I'm not sure if it makes sense to get another NVME drive to use on another PCIe slot, or just to get an SSD to put in one of the drive bays.

Thanks for any insight,

DD

I am not so much into benchmarking, so I did not test it on Aja yet. I have the same blade. I used to have it in the PX1 as well. I did run out of PCI slots, so I put the 951 AHCI and an older 941 HyperXPreditor out of its adaptors and on one single I/O Crest dual card. It Works great and it runs on its PCI slot limit that last time I checked it with BlackMagic speed test (1350/1440 or so) Also in slot 3 here, cant block those fans on the Vega VII.

 

[dickiedunn]

Thanks Alex,

I was thinking a dual (or quad) PCIe card might be my next upgrade. That way I could still mount this old SM951 on it as a boot volume and perhaps put a newer NVME card on as a scratch disk/more storage. From reading the wiki on NVME cards here, my understanding is that with a switched card like yours, you should be getting 3,000 MB/sec. Did I miss something, or why wouldn't your blades run faster than 1,440?

Also, I'm concerned about fan noise. Is the I/O Crest card fan noticeable?

 

[tsialex]

SM951 has a TRIM problem, it won’t work after the blade is full. Please note that it has nothing to do with macOS TRIMFORCE. It’s a Samsung Firmware problem never resolved.

From time to time you have to boot single user and run fsck -fy to force TRIM, after that your performance goes back to expected levels.

Do a search, this have been exhaustively discussed here.

 

[dickiedunn]

Thanks for that info. Quick question, when running the -fsck -fy command, will that erase the drive?

 

[Objectivist-C]

No.

 

[AlexMaximus]

Thanks Alex,

I was thinking a dual (or quad) PCIe card might be my next upgrade. That way I could still mount this old SM951 on it as a boot volume and perhaps put a newer NVME card on as a scratch disk/more storage. From reading the wiki on NVME cards here, my understanding is that with a switched card like yours, you should be getting 3,000 MB/sec. Did I miss something, or why wouldn't your blades run faster than 1,440?

Also, I'm concerned about fan noise. Is the I/O Crest card fan noticeable?

The speed limit comes from the PCIe slot. You can only have faster speeds in slot 1 or 2. Every other slot stops at 1530 or something. Even already with a dual card I would block most fans in slot 2 and restrict gpu cooling down n the Vega VII. I could move the gpu in slot 2 as well, but I would loose a full slot and the already hot ssd would get heat from a hot gpu backplate. In my opinion it was best to keep the AHCI drives with the configuration I have and not buy any NVME drives because of this heat/slot/pcie speed obstacle. The fan on the crest card is absolutely necessary, the heatsink really gets warm. I am amazed how much heat those two AHCI blades produce. The noise level is on paar with the rest of the standard fans in the case. For me it’s hard to distinguish the ssd fan over the pcie case fan or those three fans on the Vega VII. If noise is a huge factor, you might want to check the fan replacement thread here. When it comes to a four blade setup, the highpoint or amfeltec card seems to be the way to go. The new sonnet card will work as well, however there you will be limited to a very view ssd Typs only. I heard it takes one sided ssd blades only..

 

[SoyCapitanSoyCapitan]

SM951 has a TRIM problem, it won’t work after the blade is full. Please note that it has nothing to do with macOS TRIMFORCE. It’s a Samsung Firmware problem never resolved.

From time to time you have to boot single user and run fsck -fy to force TRIM, after that your performance goes back to expected levels.

Do a search, this have been exhaustively discussed here.

This. And it is OEM so nobody could update the firmware manually without assistance from a big name PC builder.

 

[dickiedunn]

Thanks everyone and apologies for not doing a better job searching the forum first.

I ran fsck -fy as tsialex recommended and it did seem to help, but didn't bring the SM951 to full speed. Perhaps that's just how it is when it's this full.

Thanks again. I guess my next step is to look for a bigger blade (since I'm getting full) or keep this one as a boot blade and get an NVME one for scratch/storage.

 

[dickiedunn]

Well, that didn't last long.....after a few days, I'm back to 494 MB/Sec write times.
How often does one have to run this force trim code on the SM951?
Maybe it's time to just buck up and replace with an NVME card, but that involves upgrading to Mojave, which requires, updating the boot rom and a new gpu, and...... sigh.

 

[dickiedunn]

Dumb follow up question as I still seem to have very slow write speeds even after running the force trim command after booting in single user mode (command-option-r). How do you know the command is running on the SM951 blade? Do I have to specify the drive first in terminal before typing in fsck -fy?

I just keep getting 200 MB/sec write and 1297/sec read speeds.....

 

[tsialex]

Dumb follow up question as I still seem to have very slow write speeds even after running the force trim command after booting in single user mode (command-option-r). How do you know the command is running on the SM951 blade? Do I have to specify the drive first in terminal before typing in fsck -fy?

I just keep getting 200 MB/sec write and 1297/sec read speeds.....

Single User Mode is Command-S, Command-Option-R is Internet Recovery that only MP6,1 have. You can read about Mac startup key combination with this Apple Support article.

This is a workaround for a firmware problem and it's not an intended use for the fsck command, but people noticed that it works a long time ago and we have been doing it since with success.

When running fsck -fy from Single User Mode, it only check/repair the root filesystem, so you have to boot from the SM951 and the filesystem have to be HFS+, fsck -fy don't work for trimming the cells if the file system is APFS. I have several SM951 blades, when I need to restore throughput first I do a full backup, then I clone a High Sierra install to the blade, expand the filesystem to the whole blade (I have 128, 256 and 512GB blades) and finally boot Single User Mode and do the fsk -fy command.

Btw, use DriveDX and check what is your current Media Wearout and Wear Levelling Count, maybe your SM951 is overused.

 

[dickiedunn]

Once again, tsialex to the rescue. Thank you! Somewhere I read Command-s was single user mode. After using Command-s, I ran the fsck -fy command. When it was done I typed "exit" to boot the system. Aja showed instantly faster write (>1,000) times, but as it kept going I ended up at 357. Better than the 146 I got before running the command, but very short of the 1444 read times I'm getting. I'll take a look at DriveDX to check the count and get back to you....Perhaps it is because I only have about 40 GB free on a 512GB blade.

Thanks again for your help!
[doublepost=1565737365][/doublepost]Ok, I ran DriveDX and it says all is good. Wear leveling Count is 95 (97 percent) and Media Wearout is 99 (99 percent). Seems to look ok?