Slow disk writes in RAID1 and RAID5

Good morning.

You may want to change your controller to read ahead, write back for optimal performance.  This is the suggested setup for our controllers.   Let us know the results after making the changes.

Regards,

Thanks for your reply. PERC H310 only gives me the option for No Read Ahead and Write Through

To get better performance you'll probably want to upgrade to a PERC H710 as this has a battery and cache allowing you to enable write back cache, which will most likely greatly improve your performance.

we are also seeing unacceptable performance of a dell server with H310 and 2.5" sas disks. Read performance with raid5 is 300mb/s but write performance is only 15mb/s. On another server with H700 and sata disks, write performance with raid 5 is well above 100mb/s. In both cases this is measured with GBs of data and with OS caching disabled (dd with dsync option). Why is dell even selling these H310 controllers if performance of these cards is so bad?

"Why is dell even selling these H310 controllers if performance of these cards is so bad?"

1. Because it is half the price and it fits the bill for those cost-cutters who might otherwise cuss Dell for not offering "affordable" solutions (no offense, but why did you buy it?).

2. Because it probably gives them leverage to charge more for their decent controllers.

3. Because it supports non-RAID/JBOD; the H7x0 controllers do NOT support non-RAID, so it is really the only option for those seeking a non-RAID solution.

I really wish they would 1) not market it as a "PERC" - it is an insult to those "real" controllers, and 2) market a non-RAID SAS HBA as their ONLY alternative to their "real" RAID controller for those needing a non-RAID solution.  These low-end controllers give Dell hardware a bad reputation ... in my opinion.

Unfortunately we bought it because we assumed a minimal quality/feature level because of the PERC brand name. It is a mistake we will never make again. Next time, always check the specs and if possible by something we already have in production. At minimum I think Dell should issue a warning message fo rthis Dell controller is that it is missing essential feature for running for instance high performance database applications.

"I really wish they would 1) not market it as a "PERC" - it is an insult to those "real" controllers, and 2) market a non-RAID SAS HBA as their ONLY alternative to their "real" RAID controller for those needing a non-RAID solution.  These low-end controllers give Dell hardware a bad reputation ... in my opinion."

Second this...I would like to have heard the discussion between the Dell engineers and Marketing as to these "maybe raid " cards, what a bad move Dell Marketing made.

" Dell should issue a warning message for this" like..  !!!STOP!!!   .DO NOT EXPECT PERFORMANCE IN ANY FORM FROM THIS CONTROLLER OPTION!!! , use this only if you enjoy continuing frustration, and like laying out extra cash for a real raid controller .

We have the same problem and we are clearly dissapointed.

That controller is giving us a horrible performance under write operations. It does not make sense that Dell sells this kind of hardware and it is not acceptable.

http://en.community.dell.com/support-forums/servers/f/956/t/19513222.aspx

We are talking about servers, they should provide a good performance. No one in his right mind would go for that option just for saving 180$

Our server is a dell R320 where the Raid controller is integrated and non integrated perc adapter are not supported:

http://www.dell.com/learn/us/en/04/campaigns/dell-raid-controllers?c=us&l=en&s=bsd

I think your concerns are valid.  We are looking at replacing our existing server with a Dell or HP Server.  But I would not want to purchase from a vendor who would sell us an inadequate configuration. I would be afraid that if its possible to make the mistake with this component, what other components might put us in the same situation?  Hard Drives? RAM?

Hello Daveosac,

In my case they are still investigating the problem, so I prefer to be cautious until they give me a formal response.

Right now we have compared a 3 years old hp server (raid 5) and the new one (raid 5 too). sequential write performance is 7 times better on the old one. Sequential read time is 2 times better on the new one (iometer using dell metrics).

If they finally answer that the performance is normal for this perc (h310) then I can say that is not acceptable for a production server (It takes about 30 minutes for creating the 10GB initial file by iometer against the 2,5 minutes on the old server) and we will consider changing the perc to the H710 model (cache).

Anyway I am optimistic (or I hope so) and I will wait until they finish the analysis (Fortunately they move forward to an exhaustive/in depth analysis).

Regards.

I am confused now.

We have replaced the card with a Perc H710 mini and can confirm that it solves the performance problems. We are now getting excellent sustained write speeds for large files (simple dd test) with write speeds in the order of 200-300MB/s.

Hello,

We have connected to other Site Dell server that is using the same PERC H310 (It was installed by other partner 6 months ago)

Our local technician did not report any problem because most of the information is on the external storage managed by other controller.

We have run iometer on the local disks (Raid 1 H310) of that server and same result (horrible write speed), so we are thinking in H710.

Raid 1 performance nearly the same than Raid 5

Regards.

I am confused now.