P-7805U Disappointing RAID 1 read performance

So i managed to change over to raid-1.. after the 2 hour raidset rebuild everthign looks and works well.

Running both hd tach and hd tune, i am getting just under 80MB/s on teh fast side and 40MB/s at the end of the raid set.

on read i was expecting closer to 125 MB/s

Is this normal for the intel matrix raid? most raid 1 setups that I am used to will use both drives on read. this seems to only be using one, or the performance is just bad.

I did check the matrix storage console to make sure that both drives are in the raid set and the raid set is healthy. also confrmed that in the raid bios.

I did not do an hd tune or hd tach while it was a single ACHI drive setup, so i dont have anyting to compare it to other then others performance numbers.

any thoughts?

 

Raid1 isn't regarded as a fast configuration, that would be raid0. With two of those scorpios in raid0 my Read average is usually about 95. Your numbers sound pretty accurate.

 

I'm surprised you find it disappointing or expect performance from RAID 1, RAID 1 is not for performance but insurance.

 

Let me explain so your less surprised.

to be accurate

raid 0 provides spanning.
raid 1 provides mirroring.

any performance gains are a matter of implementation of the raid.

In most cases, raid 0 is leveraged to gain both read and write performance by reading both drives at the same time, and writing to both drives at the same time. This is not part of the specification of raid 0 however. we have come to expect it.

In the same vain, raid 1 must write to both volumes in the raidset for mirroring so there is no possibility for performance gain on write. However, it can access from both volumes simultaneously on read. As with raid 0, this is not part of the specification, however it is how most hardware raid implementations work, and a performance increase on read has become an excepted norm for hardware raid.

So my question is strictly on this implementation of raid 1. Is this the normal performance?

I remain disappointed. I'm hopeful that there is a correction to this.

 

I'm avaraging 60 on raid 1 read with to scorpio's - i have to think thats above the avarage read speed for a single drive. I just get the feelign theres somthing not right with the configuration. i may see if i can change ncq and see if it makes a diffrence.

 

The OP is correct in saying RAID 1 provides *some* read performance improvements. However, I wonder why you wouldn't just setup RAID 0 (which is much faster for read times) and then use an external eSATA for backups? Is there a reason for the mirroring - other than data backup? In my experience, RAID 1 isn't exactly great for data recovery even in the best of circumstances.

 

raid 1 works for me becasue I do not need the extra space and I do not need the extra write performance. I do want the redundancy in case of a drive failure and the extra read performance. For me, I have not had raid 1 let me down, and I work in a fairly large data center, so I see my fair share of drive failures. I am used to working with dedicated raid controllers however, so this is a bit of a departure for me.

 

Raid 1 is obsolete. There is no point in having it in a laptop. Let me explain -

The idea of having Raid 1 is that you get data safety (and like you said, some read performance, but I will get into that after). However, over the past couple of years, external hard drives have become extremely large and extremely cheap. Not only can you get MORE SPACE for backup, and for LESS MONEY using an external hard drive, but you will also have more safety. The idea of using an internal hard drive for data backup is a bad one in the first place, especially on a laptop. It is very likely that if one of your drives is going to fail, both drives are going to fail at the same time. This is because accidental damage to laptops (spilling coffee on the keyboard, dropping the laptop) is more often responsible for hard drive failure than is failure due to hardware defect. This means that it is more likely that both drives fail at once than just one at a time.

If you've backed up your data with an external hard drive, you won't have that danger, and you will also have gotten a better size/cost ratio. Furthermore, you free up your second hard drive for Raid 0, more speed in both read and write, and double the capacity. Even if you don't need the extra space or extra write speed like you said, you seem to be concerned about read speed, which will be much better with Raid 0.

Which brings up your disappointment with the read speed. Many people think that Raid 1 speed should be the same as Raid 0 speed, considering that in both types you're reading the file off of 2 drives. The way it works is a lot more complex than that, but put simply, Raid 1 has the entire file on both drives, while Raid 0 has parts of the file on both drives. As you can imagine, it is easier to take two pieces and put them together, than it is to take two copies, split them up into pieces, then put those pieces together, which is not much faster than simply reading a copy from one of the drives.

Hope that helps..

 

Yes, like the others, I'd say put those things into raid0 and use a backup drive. There are external 500's that you can keep in your pocket these days. Hopefully you haven't put too much precious data on your computer though, I hate having to fresh install.

 

Thanks for the clarification =)

 

What can i say i am a bit spoiled with server raid controlers. they do get close to raid 0 performance on read. however a server environment is a bit diffrent as the qio depth is usualy high. so they can not only split the i/o between drive channels but split seqential io read ahead across chanels. pretty easy to do if you consider they are mirrors and the next read is at the same location on both drives. then again with multople qio's going on and deep cache, its a bit diffrent then a workstation.

That beign said, it seems the only way to get good read performance from this raid controller is to go raid 0.

I can live with that...cant blame me for wannting it all lol.

I already have external storeage, its not a big deal to back up, just a pita to do on a regular basis, which i know i wont do...but at least i have an image of the system as it came out of the box.

I tried turnning on and off ncq and it made no significant diffrence on the benchmarks, it may under load though. I'm to lazy tonight to play with tests with diffrent qio depths.

Sounds like i may be moving to raid 0 though.

 

Are the HDD's you are using the stock 5400's?

 

P7805-u's are stock with a 7200 RPM 320 Gig drive........

 

pair of wd scorpio black's - 7200rpm 16MB cache 320GB

 

This isn't abnormal for intel's matrix raid, you gain virtually 0 read speed in raid1 with it. As you stated higher end controllers with lots of concurent I/O operations do see a major benefit, matrix raid definitely does not. You aren't gonna get squat for performance unless you switch to RAID0 on these notebooks, RAID1 is a waste unless you have REALLY important data that you need to have live all the time, and frankly if you do, a notebook still isn't the right place to keep that data, lol. Maybe one of these days someone will cough up a 4 1.8" SATA drive notebook with a decent raid5 controller and it'll destroy all comers. Until then, raid0 is still pretty extreme for something you carry around with you in a bag.