RAID 10 - 01

In the very beginning of the article we have already said a few words about the major differences between RAID 10 and RAID 01 arrays. Namely we said that 01 and 10 RAID arrays provide both: high performance and reliability, however, not forever. If any of the 4 HDDs breaks down, RAID 01 will degrade into RAID 1 and RAID 10 - into RAID 0. In other words, the system will keep working but will either slow down considerably or no longer guarantee the data on the drives is as safe and sound as it used to be.

In other words, RAID 01 is none other but RAID 1 though applied not to separate hard disk drives but to groups of hard disk drives (2-3 units in our case), which are united in RAID 0 arrays in their turn. And RAID 10 does just the opposite, i.e. it applies Striping to RAID 1 arrays. In this review we won't touch on the practical differences between these two array types, because Adaptec and Promise controllers tested can do only RAID 01 while 3ware controller can do only RAID 10. And since all these controllers show different performance, it is hardly possible to conclude which array type is better for this or that particular application field.

3ware Escalade 6400

Of course, it was not for nothing that 3ware Company selected RAID 10 configuration to be implemented in its controller. This mode allows using TwinStor technology. As we have just seen, this technology proved very efficient in case of RAID 1 array. Now let's see if TwinStor Technology will work for RAID 10.

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Really, average access time was almost the same ad in case of RAID 1 array, but the read and write speeds have increased. Now we will try to figure out if it will tell on the results in WinBench 99.

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The outcome in WinBench appeared a little bit worse than by 2 HDD RAID 0 array. So, it appears that TwinStor technology showed its best only in Disk Trasnfer Rate test.

Now we would like to compare the performance of the controller for RAID 10 with the results obtained for RAID 0 array composed of 2 and 4 drives.

If the requests are not too numerous, RAID 10 proves as fast as RAID 0 for 4 hard disk drives. And if the workload rises, RAID 0 for 4 drives turns a bit faster. Note that RAID 10 appears closer to RAID 0 for 4 HDDs rather than to RAID 0 for 2 HDDs independent of the workload.

The picture repeats here in general.

Everything is absolutely correct, the more write requests turn up, the closer appear RAID 10 results to RAID 0 for 2 HDDs, because TwinStor doesn't work for writing operations.

Again everything is quite logical: in case of RAID 10 the controller has to transfer twice as much data via the controller bus.

And with a block size of 256KB, the picture turns out even more exciting. While there are few requests, RAID 10 is twice as slow as RAID 0 for 4 HDDs. However, as soon as the number of requests grows up to 16, its performance drops down to almost a half of that by RAID 0 for 2 HDDs. It is probably the controller bus that gets overloaded by duplicating commands sets inside the mirror arrays.

Adaptec AAA-UDMA

Adaptec AAA-UDMA controller supports RAID 01 array only. Although the end user may see no great difference between RAID 10 and RAID 01, it still exists. And it's a pity we won't be able to dwell on it here. Anyway, let's return to our tests.

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Now that you've seen all the numbers, let's make some comparative analysis. We will compare RAID 01 with RAID 0.

Adaptec AAA-UDMA controller still doesn't give a damn about the type of supported RAID array…

The only remarkable thing here is the fact that RAID 01 and RAID 0 for 2 HDDs prove faster in case of 16 I/Os than RAID 0 for 4 HDDs. Other than that the picture is really aggrieving. Only when the workload is relatively low the requests are processed a bit faster than by a single HDD with an ordinary UDMA controller. But as soon as the workload starts growing, RAID 01 on Adaptec AAA-UDMA appears comparable with the performance of a single hard drive.

Yes! RAID 0 for 4 drives managed to get a bit ahead of the competitors…

In the SequentialWrite pattern, RAID 01 needs just a very little bit to catch up with RAID 0 array of 2 hard drives.

Additional workload falling on the controller during RAID 01 implementation resulted into the general lowering of the performance compared with RAID 0 for 2 HDDs.

So, RAID 01 on Adaptec AAA-UDMA controller does work and sometimes its performance is pretty predictable even. However, what we saw in FileServer, WorkStation and DataBase patterns makes further use of four-drive configurations hardly reasonable, since the performance gain provided by RAID 01 array doesn't make up for the expenses.

Promise SuperTrak100

Adaptec and Promise controllers proved very close to one another in terms of performance, according to the previous benchmarks. Now we'll check how good RAID 01 is on FastTrak100 controller from Promise.

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The read speed provided by the controller is limited by relatively slow cache. However, the write speed looks not bad at all.

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In fact, we didn't notice any performance gain when the number of the HDDs connected to the controller increased. Supposedly, it doesn't tell on the performance at all.

No doubt, this controller will never suit for work with Windows applications.

As we can see, the performance of RAID 01 array with any number of HDDs is limited by the performance of the Stripe-group this array is based on. In case of higher workload, RAID 0 for 3 HDDs turns faster than RAID 01.

And in this pattern, RAID 0 for 3 drives can't boast the advantage over other testing participants as big as in the previous case.

The remarkable thing about this pattern is the failure of RAID 0 in case of lower workload. RAID 01 takes the lead then.

Please, pay attention to some really strange behavior of RAID 01 array for 6 hard disk drives. This array is made of two groups, each including 3 HDDs. Each group is an ordinary RAID 0 array. So two of them are united into RAID 1. Theoretically, the results obtained for RAID 01 made of 6 HDDs were expected to be much worse than those for 3 HDD RAID 0 array (since extra time is required to duplicate the commands for the second stripe group. However, under large workloads RAID 01 performs close to RAID 0 for 2 hard drives and RAID 01 for 4 hard drives. It seems to be the controller bandwidth that limits the performance then.

Well, we have already commented on graphs of the kind. Nothing new to say here.

We have to admit that Promise controller didn't show very high results. Moreover, its performance doesn't at all depend on the number of hard disk drives connected to it at all.

Controllers Comparison

To tell the truth, comparing the performance of RAID 01 - 10 configurations in WinBench tests doesn't make too much sense to us. That is why we dare omit them here, as simple as that. All the results are available in tables, so if you like you may make the graphs yourself :-)

But Intel IOMeter results may be quite worth considering.

Of course! This is exactly what we have expected!

The gap gets even larger due to the increased size of the data block used. 3ware controller appears far ahead of its competitors.

The growing number of writes slightly slows down Escalade 6400 with its TwinStor technology and the gap gets a bit smaller.

The interesting thing about it is that RAID 10 by 3ware appears slower in RandomWrite pattern than RAID 01 by Promise and Adaptec. The leadership of Promise with a 6 hard disk drive array is quite logical, since it has the largest stripe group of all (made of 3 HDDs) and the write requests do not get into its slow cache.

In SequentialWrite pattern where we test the controllers' bandwidth 3ware is again in the leading position. Some of you may think that we forgot to add the graph for RAID 01 by Promise SuperTrak100. However, believe us, it is there. You simply don't' see it :-)

All in all, 3ware deserves the laurels on this stage, having been the fastest in the four patterns out of five.