Intel X25-V in RAID-0: Faster than X25-M G2 for $250?
by Anand Lal Shimpi on March 29, 2010 8:59 PM ESTMissing TRIM - Does it Matter?
Clearly the performance of two X25-Vs in RAID 0 is great, but you do lose TRIM - isn't that a dealbreaker? Honestly, it depends. For sequential accesses, TRIM isn't necessary on the Intel drives. The X25 controller does a good job of aggressively cleaning and recycling NAND blocks and you'll pretty consistently write at peak performance if your workload is almost all sequential.
The more random your access pattern is, the more you'll miss TRIM. Thankfully desktops don't spend too much of their time randomly writing data across the drive, but I'd say a good 30% of most desktop writes are random to an extent. Over time, these random writes will build up and bring down the overall performance of your RAID array until you either secure erase the drives or write sequentially to all available free space.
There is one other option for curbing the performance degradation before it happens. Remember the relationship between spare area and write amplification:
The more random your workload, the higher your write amplification (and thus the lower your performance, shorter your NAND lifespan). Increasing spare area can go a long way to reducing write amplification. While it can't eliminate it, it can definitely make a dent.
If you're looking to keep performance as high as possible with a pair of X25-Vs in RAID, you can always allocate more NAND as spare area. Secure erase each drive, create your RAID array, and then create your partition on the drive smaller than max capacity (try 10 - 20% smaller). The unpartitioned space should automatically be used by the controller as spare area. To test the effectiveness of this approach I took an X25-V, filled it with garbage data, and then wrote random data across the drive as fast as possible for 20 minutes. I then ran HD Tach to get a visualization of write latency (expressed by sudden drops in bandwidth) vs. LBA:
A standard 80GB X25-M wouldn't be this bad off, the X25-V gets extra penalized by having such a limited capacity to begin with. You can see that the drive is attempting to write at full speed but gets brought down to nearly 0MB/s as it has to constantly clean dirty blocks. Constant TRIMing would never let the drive get into this state. It's worth mentioning that a desktop usage pattern shouldn't get this happen either. Another set of sequential writes will clean up most of this though:
Intel's controller is very resillient. Even without TRIM, as long as your access pattern has some amount of a sequential component you'll be able to eventually recover performance.
Now look at what happens if we only use 60GB of the 74.5GB RAID 0 array upon creation and run the same test:
Performance isn't nearly as bad. That added spare area really comes in handy. Of course another pass corrects nearly everything:
If you don't need the added space, using a smaller partition is a great way to ensure high performance for as long as possible. The effectiveness of this approach is a difficult thing to benchmark given that it's only after months of normal use that you get enough random writes to the drive to be a problem. The good news is that even if you bombard the X25-Vs with random writes, the drives can quickly recover as soon as they're hit with some sequential data.
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jed22281 - Friday, April 2, 2010 - link
@GullLarsCould you please explain to RoomRaider (down the bottom of pg 6) that there is no
TRIM support for RAID-0?
He keeps insisting there is throughout these comments....
He needs someone to explain why what he's citing as proof, is wrong.
Thanks if you can!
jed22281 - Friday, April 2, 2010 - link
Then again maybe he's right...http://www.tweaktown.com/articles/3116/tweaktown_s...
But his cited no's for knowing this to be true haven't sounded right to me yet.
Boofster - Tuesday, March 30, 2010 - link
It would be nice to see the X25-M G2 in RAID0 as well. Yes it is much more $ but still great value if you look at the performance. The 160gb will cost you ~$400 and possibly beat anything in this review. Of course you can say the same for the faster single drives in RAID0 as well but the value is lost.I can say for sure the Intel RAID tools do not let you TRIM the drive in RAID0 (X58 board). I am not sure if you temporarily drop the drive from the RAID, TRIM it, then put it back will work. Probably not because it will mess up the file system. I really hope Intel works this into their drivers as it is a very attractive option.
Can you also elaborate on the cleaning process? How do I accomplish this "secure data wipe"?
Hauraki - Tuesday, March 30, 2010 - link
There was a review on X-bit labs praised the v+ 2nd gen for home usage, and I'd like a second opinion from AnandTech. Thanks.nobita1168 - Tuesday, March 30, 2010 - link
Hai, i miss printed version , i like save to disk and read later, can anantech make a print version again? thanks
Ramon Zarat - Wednesday, March 31, 2010 - link
I don't know if the question has been asked before, but I'm wondering if TRIM will eventually be implemented for RAID or if it's technically impossible. If it's possible, any clue as of when it will happen?jed22281 - Saturday, April 3, 2010 - link
I would love to know this too! :(Roomraider - Wednesday, March 31, 2010 - link
After reading this review, I had to post: I'm running 2xM 160 g2's in Raid-0 with full trim support from Intels latest chipset drivers designed just for trim to raid support.So what gives here? Did someone not get the news about the new chipset drivers?
jed22281 - Saturday, April 3, 2010 - link
You are mistaken, there is not support for drives combined into RAID volumes.There is for individual drives connected to the controller while it's in RAID mode.
http://www.intel.com//support/chipsets/imsm/sb/CS-...
Also see
http://communities.intel.com/community/tech/solids...
Look for the gold star at the top of the page, select show details and then go to announcement 2.
"Intel® RST 9.6 supports TRIM in AHCI and pass through modes for RAID. A bug has been submitted to change the string that indicates TRIM is supported on RAID volumes (0, 1, 5, 10). Intel is continuing to investigate the ability of providing TRIM support for all RAID volumes in a future release."
buzznut - Thursday, April 1, 2010 - link
Thank you Anand!This is exactly what I've been looking for. I thought the performance would be better, but I had no idea it would be this good! I still see very little being written about these cost effective little drives. its good to know where to go for my SSD advice.
A quick question for anyone- My motherboard was running the drive (Intel x25-v) in ahci mode, but the mobo( Tforce ta790gx a2+) has never liked running in that mode and I started getting BSOD's after about two weeks. I had to switch back to ide mode, the board has always been quirky this way. Runs very smooth in IDE mode, no problems.
I had heard someone mention that trim doesn't work in ide mode, only while running the drive in ahci. If this is the case, then I will truly not miss trim when I get another drive and raid!
Can anyone confirm the loss of trim command in IDE mode? The intel toolbox seems to work just fine when I run the weekly optimizer.