2 Vertex SSD's in RAID not as fast as I hoped...

[unSOUND]

This is my first post here, so I'll begin with an introduction... :)

I have a Mac Pro ( Early 2008, 8 x 2.8 GHz ).
In this Mac Pro I have 4 WD Caviar Black drives ( in the normal drive bays )
And 2 OCZ Vertex drives ( 30 GB, both placed in the Superdrive bay )

The 2 Vertex drives are connected to the 2 extra SATA ports on the motherboard. The ports are SATA II.

When I do a speed test with Xbench, the disks have a top speed of about 230 MB/s. However, when I make a striped RAID with 2 Vertex SSD's, the combined speed doesn't get above the 330 MB/s... I already tried different block sizes... Anyone have an idea where the problem might be located ?

Thanks in advance !

[unSOUND]

* UPDATE *

OK, this sucks. It seems one of the 2 drives has somehow become much slower. When I tested them again, it seems that one drive has a top of 230 MB/s, but the other one has a top speed of 100 MB/s... I tried diferent cables and different SATA ports, so it really seems to be the drive itself... But dispite the low speed, the drive itself seems to be functioning witout any problems, just slower...

Any ideas ?

[harshw]

* UPDATE *

OK, this sucks. It seems one of the 2 drives has somehow become much slower. When I tested them again, it seems that one drive has a top of 230 MB/s, but the other one has a top speed of 100 MB/s... I tried diferent cables and different SATA ports, so it really seems to be the drive itself... But dispite the low speed, the drive itself seems to be functioning witout any problems, just slower...

Any ideas ?

Reset the slow drive by formatting in Windows, wiping with wiper.exe. What's the firmware on both drives ?

[unSOUND]

that's going to be difficult, since I don't have Windows on any of my machines... Both drives have firmware verion 1.3 by the way.

[jmcgeejr]

Just flash the slower drive with 1.3 firmware it will reset the drive (all data as well)

[RyderOCZ]

Just flash the slower drive with 1.3 firmware it will reset the drive (all data as well)1.3 does not erase or reset the drive.

[unSOUND]

I went back to the store where they tested both drives. One was functioning normal at a steady speed of 220 MB/s, the other one seemed to be quite irradic. Sometimes it would act normal, and sometimes it would go slow. So I got a new one.

I placed them both in my Mac Pro, and apart they both function well, both have speeds above 200 MB/s. In Striped Raid however, the combined speed stil stays below 350 MB/s... weird.

[eyvind]

I placed them both in my Mac Pro, and apart they both function well, both have speeds above 200 MB/s. In Striped Raid however, the combined speed stil stays below 350 MB/s... weird.

Um, isn't 350MB/s about the max transfer rate of SATA at 3Gb/s? Maybe not so weird :)

[unSOUND]

If they were connected to one port it would be logical... But they are connected to seperate ports... Unless the ports are connected to the same path on the logicboard, that I don't know for sure...

[harshw]

If they were connected to one port it would be logical... But they are connected to seperate ports... Unless the ports are connected to the same path on the logicboard, that I don't know for sure...

Try doing a test with 'dd' to check the sequential speed

[unSOUND]

Vertex 1:

Uncached Write 213.59 MB/sec [4K blocks]
Uncached Write 136.31 MB/sec [256K blocks]
Uncached Read 41.54 MB/sec [4K blocks]
Uncached Read 191.57 MB/sec [256K blocks]

Vertex 2:

Uncached Write 229.88 MB/sec [4K blocks]
Uncached Write 103.23 MB/sec [256K blocks]
Uncached Read 41.82 MB/sec [4K blocks]
Uncached Read 169.45 MB/sec [256K blocks]

I can't test the speed in RAID right now, since I'm using them seperate at the moment... But when they were in RAID the uncached write speed of 4k blocks was about 330 MB/sec.

[Tony]

looks to me a quick run over with sanitary erase in a windows machine would get those drives upto equal speeds.

Make sure both drives are running FW1.3, this FW has advanced garbage collection and handling that may help also.

Raid is always going to slow down till TRIM is implemented...in an apple me personally i would not bother

[unSOUND]

Both drives have firmware version 1.3

I don't have a Windows machine, and neither do any of my friends for that matter. So Windows tools are not possible. And since OCZ is now selling expensive "Mac-ready" SSD's, I personally think it's time they earn that extra money by providing the nescessary tools for OS X.

At the moment I use the drives as single drives, one for Tiger and one for Leopard. I might as well keep it this way...

[drshdw]

http://www.ocztechnologyforum.com/forum/showthread.php?t=57549

Sticky?!

[unSOUND]

Those are just the FW updates, I'm talking about a Mac alternative to the wiper.exe and such other tools...

[Praz]

And since OCZ is now selling expensive "Mac-ready" SSD's, I personally think it's time they earn that extra money by providing the nescessary tools for OS X.
The difference in price is a small amount for the Apple certification costs with the rest the result of the price being inflated at the retail level.

[unSOUND]

No matter where the difference in price goes, if you want to sell things with an Apple logo on it, you should also provide the support and nescessary software. Telling people to "grap a copy of Windows" is not my idea of supporting Macs.

[harshw]

Those are just the FW updates, I'm talking about a Mac alternative to the wiper.exe and such other tools...

Well there can be no alternative to wiper and other tools on OS X 10.5. That's due to APPLE's AHCI SATA driver limitations rather than anything else. The ability of wiper to work depends on the application being able to send arbitary ATA commands to the AHCI subsystem. This cannot be done with the current framework in OSX unless Indilinx and OCZ reverse engineer the SATA kexts and provide their own kexts to subclass the existing ones - something that Apple would never condone or support.

According to one of the more knowledgeable people on the forums (a former Apple dev), the 10.6 framework provides the necessary hooks so tools such as wiper - and hdparm - will be possible at last.

330 MB/sec is a bit low for RAID0 and two Vertexes. This could be due to
a. Stripe size
b. Alignment ( and offset) for the partition
c. The way the HFS+ filesystem formats the RAID partition

Could you check these variables and report back ?

[unSOUND]

1]I tried several sizes, from 16 kb to 256 kb. No difference.

2]I have no idea how to check this

3]I used HFS+ journaled, with GPT scheme


I also did a full erase with OS X' Disk Utility, both drives now have the same speeds. ( Max 255 MB/s ). But when combined as a RAID 0 they still provide 330 MB/s. However, some other values are doubled in speed...