Raid 0 Performance

[diamondmines]

Hi,

I have a raid-0 system with 2 kingston v+200 seriess ssds and I get around 400mb read write speeds. I believe I should be getting more but I think there is a bottleneck. I have watched other people's videos on youtube and they get around 900mb or even 1gb read/write speeds even on 2x 60gb ssds.

My system is
Intel Core i5 2310 2nd Gen.
Asus P8H67-MLE
Kingston 8gb 1066Mhz DDR3
XFX 7750 1gb 128bit

Can you also give me some advice to enhance the performance of raid-0?

Thanks in advance.

[jim]

They're probably using dedicated RAID cards. I assume you're just using the motherboard?

For what it's worth, unless you have a highly specific requirement, this is making virtually no difference to the speed of your PC.

[kalniel]

Basic stuff to check is that you plugged into the grey ports and you are using the latest intel controller drivers.

A software RAID probably won't be as fast as using dedicated hardware controller, but check that you are using the same benchmark settings as well - being a sandforce controller speed on non-compressable data will be quite a lot lower than compressable.

From the Hexus review here:
http://hexus.net/tech/reviews/storag...-120gb/?page=4

I would fully expect you to be seeing what look like lower speeds on some benchmarks - they're only getting 145mb/s write speed on that test for a single drive, so 400 in RAID 0 would be good. Change the test pattern to something like all 0s and you'll see the score jump up.

[diamondmines]

kalniel,

test pattern meaning like stripe size?

Its 128KB by default.

[diamondmines]

Also, I understand that a raid card costs like hell like LSI etc. If I get like 400mb for 2 x raid 0 for 120gb ssds, would i get like 800mb for 4 x ssds, again being the same ssds installed.

4x kingston v+200 series.

[peterb]

Also, I understand that a raid card costs like hell like LSI etc. If I get like 400mb for 2 x raid 0 for 120gb ssds, would i get like 800mb for 4 x ssds, again being the same ssds installed.

4x kingston v+200 series.

No, he means the pattern of bits written to and from the drive. In traditional drives it was important because of the way the data is physically written to the disk.

Multiplying disks using RAID0 double the storage capacity - not the speed. Again with traditional disks it was deprecated for most applications because if one disk fails, all the data has gone. That is still true for SSDs, although (in theory) they should be more reliable.

Lots of claims are made for speed improvements using RAID0 - I think most of them are urban myths, unless you are doing specialised tasks (such as running benchmarks! ) Personally, I'd never use RAID0 for critical data, even with a robust backup regime in place,

[shaithis]

Raid0 speed boosts are huge on SSDs, especially when you get the stripe and cluster sizes optimised for the main use of the storage.

I am currently doing some testing between a high-end controller and intel on-board and so far the on-board is holding it's own very well.....and now that you can have TRIM in RAID0 on intel controllers (requires you to mod your own BIOS at the moment if you do not have intel made mobo) I am pretty much set on using onboard until the add-in card manufacturers start supporting TRIM.

Don't forget RAID0 (especially with TRIM) will increase the life of the SSDs.

[kalniel]

kalniel,

test pattern meaning like stripe size?

Its 128KB by default.

No, as peterb suggests, the data that is being written to the drive in the benchmark. Benchmarks test speed by writing and reading data. Drives that use compression techniques, like sandforce based SSDs, will perform differently on different patterns of data depending on how well they can compress them. The more regular that pattern is, the more it can be compressed, and thus the benchmark speed for very regular patterns will be higher than test data which has no patterns and is hard to compress.

Crystal disk has an option for you to set the pattern, either all 1s, all 0s or random (default). The random setting will give a lower score than the all 1s or all 0s. So try again using all 0s for example and see if that improves your MB/s.

Don't forget RAID0 (especially with TRIM) will increase the life of the SSDs.

How does that work? 10GB of writes will put the same write load on either a single 200GB disk or two 100GB disks in RAID0 surely?

[shaithis]

How does that work? 10GB of writes will put the same write load on either a single 200GB disk or two 100GB disks in RAID0 surely?

The writes get shared. So 2 disk in raid 0 will cause 5GB of data per disk to be written per 10GB of writes...effectively doubling the life of each disks NAND.

[kalniel]

The writes get shared. So 2 disk in raid 0 will cause 5GB of data per disk to be written per 10GB of writes...effectively doubling the life of each disks NAND.

But each drive has half the write capacity/life compared to a single bigger drive.. so you don't gain anything overall.

Don't forget that in an SSD writes are spread out across the available memory - doubling that memory gives you at least as much extra life as doubling the number of drives.

[shaithis]

But each drive has half the write capacity/life compared to a single bigger drive.. so you don't gain anything overall.

Are you sure about that? and in every case?

Many drives of varying capacity have the same performance, surely they are using different NAND sizes and not doubling the number of chips.

[kalniel]

Are you sure about that? and in every case?

Many drives of varying capacity have the same performance, surely they are using different NAND sizes and not doubling the number of chips.

Yes. Just increasing the NAND size helps. It's not the number of chips that's important for write life (though that helps increase your speed as SSDs all use a kind of internal RAID, so the more channels you have the more your bandwidth).

External RAID 0 gives the same effect of more chips, so more channels, and also helps overcome any controller limitations such as a limiting SATA speed. But you pay for that in decreased reliability (and thus operational life in a way) through increased vulnerability to part failure (duplication of all the other bits of the drive that aren't NAND chips for etc.)

[diamondmines]

Thanks a lot guys, you've been a great help. And although I kind of understand what you've suggested, I am still unclear about the following:

1. Can we turn on TRIM on RAID-0? And do we do it the normal way?
2. My current strip size is 128KB. Should I decrease this to 64 or 32KB? I want better read/and write performances as well as quick loading times for programs...
3. So in general, would I benefit from 4x120GB SSDs plugged into my motherboard slots (SATA-III ports)? Or would there be significant performance difference between 2x SSDs and 4x SSDs running in RAID-0?

Thank you!

[kalniel]

1. Can we turn on TRIM on RAID-0? And do we do it the normal way?

Used to be 'no'. I'm not sure if more recent Intel drivers have changed this.

2. My current strip size is 128KB. Should I decrease this to 64 or 32KB?

Nope.

3. So in general, would I benefit from 4x120GB SSDs plugged into my motherboard slots (SATA-III ports)? Or would there be significant performance difference between 2x SSDs and 4x SSDs running in RAID-0?

Nope. You only have two sata 6gbps ports anyway.

[diamondmines]

What about the Crosshair V Formula that I am going to get with my new rig? There should be more than 2 SATA III ports?

[kalniel]

What about the Crosshair V Formula that I am going to get with my new rig? There should be more than 2 SATA III ports?

What will you be using your computer for?