Very slow SSD write performance!

[Dave T]

I have a 4 year old PC, built with 4 striped Intel X25 SSDs, with a 3ware (LSI) 9650 RAID controller. I have not run any benchmarks on it in a long time, but just ran Crystal's disk benchmark, and noticed that my write speeds are very slow. For example, I get 600-700mbps in the sequential 512kb read test, but only about 30mbps for writes (!).

Any ideas? I checked, and TRIM is enabled on the OS (Windows 7). I am not even sure if my controller supports TRIM though. I upgraded my controller to the latest driver (I think), and that didn't help.

Sorry, I am probably leaving out some relevant info. Please ask away. This computer was very expensive (over $5K). I realize it isn't quite state of the art any more, but I should be getting better performance than this!

Thanks.

- Dave

 

[ShintaiDK]

The RAID controller doesnt support TRIM.

Are you running RAID0? Is the raid controller set to write back or write through?

Also how much free space is there on the drives?

 

[Dave T]

Yes RAID 0.

I'm not in front of the computer now, but iirc, it has about 160gb free. I don't know how the writes are configured but will check. I don't know how to check that, if you do - please let me know. Otherwise I will try to figure it out.

And regarding TRIM - ugh. Do you think that's the problem? When I bought the computer, I was told that 3Ware would be coming out with an updated driver that supported TRIM. I never followed up. So they never did?

 

[Cerb]

TRIM shouldn't be a problem for the X25 SSDs, though. I suspect the RAID controller is just kind of slow, and set to no write caching. Mobo RAID 0 or Windows software RAID 0 might be faster.

 

[Dave T]

The controller is using RAID 0. I bought the controller because it was supposedly much faster than the onboard controller. Write caching is disabled though. I can't figure out how to turn it on, or if I can. In any case, the drives benchmarked much faster when they were new. So something changed. Fragmentation?

 

[ShintaiDK]

You need write caching enabled. Else it will be terrible slow.

And no, its not fragmentation. Thats for HDs only.

 

[rumpleforeskin]

Due to the lack of physical moving parts random reads/writes have the same(ish) performance as sequential ones so Fragmentation is not an issue for SSD. Defragmenting SSDs is not recommended as it adds unnecessary wear.

If you have reinstalled the operating system since the last good benchmark it may be worth checking the Page and partition are correctly aligned, this can half the write performance if not correct.

I note you have also updated to the latest drivers, maybe you could rollback to a previous driver to determine if the newer release is the cause of the problem.

 

[Dave T]

Ok - I found one thing out. The battery backup on my controller failed. So that caused write caching to not work. I can replace the battery backup (at a cost of $125), if that will help. Or I could start upgrading. Even if I get the battery backup replaced, I still have a controller that doesn't support TRIM. So should I upgrade the controller? Do you know of one that does support TRIM? Or should I just upgrade the motherboard and do software RAID 0 on the mobo?

Also, I was over at a friend's house just now, and he happened to be working on an SSD based system. I told him that I didn't have write caching turned on, and he said he didn't think it would make a difference. He did a test with Crystal, before and after disabling write caching - and the numbers were the same.

Rumple - no, I haven't reinstalled the OS, and I was having this issue before I upgraded the driver. That was why I upgraded the driver.

Any advice would be appreciated. Thanks!

- Dave

 

[John Connor]

I don't understand. I RAID controller has a battery? I know RAM drive PCI cards have a battery, but a RAID controller? Why would that need a battery?

At any rate, wouldn't the cost of a new card be cheaper than replacing the battery?

 

[Dave T]

The RAID controller has a battery for the write cache. If the computer loses power while data is still in the cache, it has the battery so it doesn't lose the cache and leave the drive in an indeterminate state due to a partial write.

I haven't priced out new cards yet. One guy told me that he doesn't know of any external RAID cards that support TRIM, so I'm not sure if I even want a card next time if I'm going to upgrade.

 

[Cerb]

When you upgrade, if you're not using >4 drives (LSi is faster with larger arrays, and supports 8 drives per controller), and if you're running Windows, use Intel's onboard. Just about any H or Z series chipset motherboard will do the trick. If not running Windows, just use software RAID.

Generally, RAID cards haven't been supporting TRIM, and over-provisioning (adding more spare area) is how the enterprise drives deal with it.

 

[Old Hippie]

That LSI card you have really isn't made for fast SSD speeds in RAID0 and I'm not aware of any external RAID controller cards that support TRIM.

The battery doesn't really matter but was does matter is for the card to support the optional FastPath chip or software.

Yours doesn't.

What you need to do is go to the LSI site and get a DL of your card's manual or write support and ask for the best RAID0 configuration for your card.

You'll need to enter the LSI configuration utility while your computer is booting and it's not really intuitive.

While you're there you may also want to change stripe size.

I'm assuming you have the 80GB X-25s and 160GBs of free space should let the GC work well and it would help to let the computer idle for a few minutes before shutting it down.

I have a 9260-4i with FastPath and although it's an older card the performance with SSDs is great.

The 9260-4i is your cheapest option and I see them for @ 280-290 on Ebay but the FastPath chip is usually @ another 150.00.