Help choosing SATA ports for SSDs with RAID 0

[pudgie]

I've got an ASRock OC Formula. It has two chipset SATA III (6 Gb/s), four Marvell SATA III, and four chipset SATA II (3 Gb/s) ports.
I have the OS (Win 7 Pro) installed on my older SSD (Crucial C300), which I want to use as the boot device (non-RAID); and I want to set up two Samsung 840 Pro SSDs in RAID 0 over SATA III ports for data. I want to be sure SSD TRIM is active.

As I understand it
(a) SSD TRIM functionality is not available for SSDs in RAID 0 unless you use the latest drivers with Intel Rapid Storage Technology (RST) software
(b) Intel RST only works on Intel's chipset SATA ports, not the Marvell ports
(c) Marvell ports are not recommended by ASRock for booting from (apparently much less efficient), although they can be used if absolutely necessary

So it seems my options are:

• boot with the C300/OS off of a (slower) chipset SATA II port, and run the Samsungs off the two available chipset SATA III ports
• boot with the C300/OS off of a Marvell SATA III port, and run the Samsungs off the two available chipset SATA III ports
• move the OS to Samsungs in RAID and run them/boot from the two available chipset SATA III ports; and use the C300 for something else

Opinions on the options?
I'd rather not have to move the OS off of the C300 to the Samsungs because it's locked to the C300. To be able to move it, I would basically have to buy another copy of Windows. I also don't trust RAID 0 in terms of reliability. I want to use the Samsungs in RAID 0 for their fast performance, but I expect that at some point they will fail; and I'd rather that not happen to the disk(s) where the OS and certain programs are.

Of the two other options, which incurs a greater preformance hit? Running the OS off of a chipset SATA II or running the OS off of a Marvell SATA III?

[havasuphto]

Re: Help choosing SATA ports for SSDs with RAID 0

I have the same MB, and you've got a furball there. You need to use 1 of the 2 main Sata III ports to boot. I'm not aware of being able to use it any other way(you read the instructions just like I did).
so, you put your boot drive on the primary Sata III, and use the yellow Marvell Sata III's for your Raid 0 drives. And, I understand you will lose Trim and rst.....just don't see a way around that.

However-I have to ask; why would you want/need Raid 0 for SSD drives??? I could understand Raid 1 through 10, but not 0. I just don't see the speed difference. IF, those 2 drives are already configured in a Raid 0 array-wouldn't moving them onto a new MB with a different controller just mess everything up, requiring a re-format to start the array?

I moved away from Raid 0 array's when I got my Intel SSD. I use it for boot/OS, and a game or 2. I use the WD HD for everything else. With my set-up, reading/writing to the single HDD is plenty fast enough, even for editing HD video on the fly(I use Avid).

also, I don't believe there is any real performance "hit" between Sata III and II. I think that's mainly marketing. Just my opinion.
Good luck.

[pudgie]

Re: Help choosing SATA ports for SSDs with RAID 0

Thanks for the reply!

Well, the user guide on the CD very strongly recommends booting from the chipset SATA ports, but it doesn't say you can't boot from the Marvell ports. And it doesn't say you have to boot from the chipset SATA III ports; it offers the alternative of booting from the chipset SATA II's.

[parsec]

Re: Help choosing SATA ports for SSDs with RAID 0

You can boot from the Intel SATA II ports just fine, just set the boot order in the UEFI/BIOS.

Some info that may help you make your decisions:

The Z77 SATA chipset, with an IRST 11 version driver and Option ROM (your board should have the correct OROM) supports TRIM in RAID 0. That is on all the Intel SATA ports. I've checked this myself on my ASR Z77 boards, and it does work. It also supports TRIM on single SSDs, with Windows 7 or 8.

The Marvell chipsets are really more (in)famous for their poor performance, with a few rare exceptions (the 9182, and perhaps some of the newer 92xx chips), than being a bad choice simply for booting. All of the Marvell 91xx SATA chipsets (except the 9182) use two PCIe lanes for their I/O, one in, and one out. Your board is PCIe 2.0 for that chipset, so that's 5Gb/s max speed, obviously not the 6Gb/s of full SATA III.

But guess what, that's not two PCIe 2.0 lanes for each SATA port, that's one PCIe 2.0 lane in and out, for the entire chip! So put two drives on it for RAID 0, and you get 2.5Gb/s for each port, less than SATA II throughput. But mother board manufactures from ASUS to Zotac, and Marvell, have boldly labeled these SATA chips as SATA 6Gb/s for years. How they can claim the 9172 chipset with four ports will operate at SATA III speeds with drives connected to two or more ports is astonishing IMO, since a single port cannot manage full SATA III speeds. The Intel SATA interface does not suffer from any of these faults or restrictions.

What about TRIM for the Marvell chipsets? For RAID, no chance, and Marvell has never stated clearly that TRIM is passed to SSDs when used as single drives. No news is not good news in this case, IMO. I need to try that new TRIM check program on the Marvell chips, just for fun.

Here's a performance comparison of the Marvell SATA 9172 "SATA III" chip to those from AMD and Intel:



Sorry for the long Marvell rant, but the apparent bold faced lie about its performance, which has fooled many users of boards with these chips, is not discussed in PC hardware review web sites much at all. If anything beyond SATA II performance can be called SATA III, then they qualify, but the clear technical realities of their design, which Marvell freely states in their documents, is to much to ignore.

Regarding RAID 0 arrays of SSDs, I've used them for years, and with good SSDs like your 840 Pro Samsung's, they'll be fine. I have many SSDs, some dating to 2010, and they all still work fine.

The comment about no real world performance advantage to SSDs in RAID 0 has some merit. The very high sequential read and write speeds of single and SSDs in RAID are only one aspect of their performance. SSDs do not constantly perform all I/O at 500MB/s. Small random file (4KB - 16KB) access speeds range from the mid 20MB/s to the mid 30MB/s, and is a common file size of Windows OS files. In RAID 0, large file sequential read and write speeds scale well, about 1.5 - 2 times the single drive speeds. The 4KB file speeds do not increase at all, and usually decrease somewhat. Overall, IMO you don't lose performance using SSDs in RAID 0, but the gains for use as an OS volume are not large.

If you work with any kind of very large files, such as image or video files, reading and writing multi-megabyte files quite a bit, then a RAID 0 volume for their storage will be faster. The only way to really learn what works the best for you is to use the SSDs in various ways. You can move your C300 OS drive from an Intel SATA III port, to a SATA II port without any problems, and see how much difference in boot time you have, if that matters to you. You can also move two SSDs in RAID 0 from the Intel SATA III ports, to the Intel SATA II ports, without any problems. The Marvell RAID format is apparently not the same as Intel's, so you can't move a RAID volume created on one chipset to the other.

The suggestion not to use the Marvell SATA interface for the OS/boot drive is likely more due to the necessity to install a driver for the Marvell chipset during the OS installation, than anything else. You can install an OS with a single SSD on the Intel ports and then move it to the Marvell ports.

[pudgie]

Re: Help choosing SATA ports for SSDs with RAID 0

Thanks for that extremely helpful comment, parsec.

I had just come across that techgage article before I read your post.

That, along with
this Tomshardware article comparing Intel SATA III vs SATA II port speeds in real-world applications
this thread from anandtech forums, comparing Marvell SATA III (SE9182) vs Intel SATA II
and your post have led me to conclude that my best option, as a starting point, will probably be to use the Intel SATA II to boot with the C300 and put the RAID 0 Samsungs on the Intel SATA IIIs.

I completely agree with the disgust at how the industry advertises these components.
You have to spend so much time reading reviews and forums and manuals before even making purchases so you don't end up feeling ripped off.
By the time you've finished doing all that prepurchase work, then waited for equipment to arrive (if you are ordering online), then dealt with incompatibilities that you had no way to predict, and dealt with defective parts that needed to be RMAd, the stuff you originally ordered is now bordering on obsolete. -- ok, there's my rant lol

Again, thanks for the input.

[pudgie]

Re: Help choosing SATA ports for SSDs with RAID 0

I have confirmed that it is very easy to boot from a SATA II port. Just switch the cable from the SATA III to a SATA II port, then modify the boot selection in the UEFI.

The switch does incur a performance hit in sequential reads though, at least using synthetic benchmarks. (I don't know how relevant that will be in real-world applications, since I haven't loaded everything up and started testing yet.)

[pudgie]

Re: Help choosing SATA ports for SSDs with RAID 0

here are the AS SSD results
SATA III on left //// SATA II on right

[parsec]

Re: Help choosing SATA ports for SSDs with RAID 0

Interesting results, I am not familiar with the performance of the Crucial C300, an earlier SSD, and at one time among the very best performing SSDs. The C300 still has above average 4K read performance, as can be seen in the AS SSD results.

BTW, IRST, which you are using (hope you installed the OS in RAID mode) has a quirk (bug) with Windows, in that Write Caching seems to be enabled in a disks properties, when it actually isn't. I don't know if you've "fixed" this already, since the 4K write speeds look low, but that may just be the C300 itself. In any disk's Properties in Device Manager, in the Policies tab, you'll see write caching checked, or enabled. With a fresh installation of IRST, it really isn't. Uncheck it and click OK. Then go right back in, check it and click OK. You should see an improvement in 4K write speeds.

If you create a RAID 0 array with your 840 Pro's, you'll find write caching is shown as disabled in the IRST UI, and shown as enabled in that RAID volume's Policies. Again, it isn't enabled. Just enable it in the IRST UI.

When you run AS SSD on your 840 Pro's, either singly or a RAID volume, you'll see a pretty big difference in the sequential speeds, among others. Seeing the C300 results really has me wondering if one or more SSD manufactures, when the C300 was available, decided to increase the sequential speeds at the cost of others. That is, all the ~500MB/s sequential read speeds that are advertised is all we see, but the majority if not all of those SSDs have less or at best equal 4K read performance that your C300 does. Only recently has the 840 Pro SSD taken us back to 30+MB/s 4K read speeds. That is with NAND chips that are 266% faster than those on the C300.

I have become increasingly skeptical about how accurate synthetic benchmarks are in gauging a SSD's performance in the real world. My Intel 520's score poorly in AS SSD (due to using SandForce controllers, and AS SSD using all non-compressible data, which is not typical of real world data) yet in use as OS drives, I detect no difference between them and my 840 Pro's, which score about twice what the C300 does.

I agree with your "rant". Most people buy hardware and hope for the best. I'm at the point where I must read a mobo's manual to see what the BIOS options are, which may be inaccurate, and changes with BIOS updates. Then one manufacture has some things I want, but not other things another manufacture has, that I want. Having the "latest and greatest" does not last long, a year at most, even with CPUs now. I recall a forum post by a guy mad at Intel, when his i7-990x CPU ($1100) was surpassed by the i7-2600K in some benchmarks, at less than 1/3 the price. He was mad because he could no longer say he had "the best"

[pudgie]

Re: Help choosing SATA ports for SSDs with RAID 0

BTW, IRST, which you are using (hope you installed the OS in RAID mode) has a quirk (bug) with Windows, in that Write Caching seems to be enabled in a disks properties, when it actually isn't. I don't know if you've "fixed" this already, since the 4K write speeds look low, but that may just be the C300 itself. In any disk's Properties in Device Manager, in the Policies tab, you'll see write caching checked, or enabled. With a fresh installation of IRST, it really isn't. Uncheck it and click OK. Then go right back in, check it and click OK. You should see an improvement in 4K write speeds.

If you create a RAID 0 array with your 840 Pro's, you'll find write caching is shown as disabled in the IRST UI, and shown as enabled in that RAID volume's Policies. Again, it isn't enabled. Just enable it in the IRST UI.

Just to be sure I am following you: at the end of doing this, under Policies in Device Manager for the RAID SSDs volume, you should have
Enable write caching on the device (checked)
Turn off Windows write-cache buffer flushing on device (un-checked)

and in IRST for the volume you should have
Write-back cache: (enabled)

Is this correct?

[parsec]

Re: Help choosing SATA ports for SSDs with RAID 0

Yes, that is the correct. Those are generally considered the standard best settings.

I have noticed a new twist on this, which some have recommended for a while now, which is checking Turn off Windows write-cache buffer flushing on device. That is the recommendation in Samsung's Magician software, in the OS Optimization feature. Since you use Samsung SSDs, you may notice this, so I'll mention it.