The culprit at the heart of these performance issues seems to be Dell's boneheaded policy of disabling the native disk cache on SAS drives, even though they seem to leave it enabled for SATA disks as a matter of default configuration for H300 level controllers.īlackhat Research pinned a nice screenshot of this language in a Dell user manual: While collective hearsay is rather convincing, I wanted to see for myself what was going on here. I didn't want to take suspicion at face value without some investigation of our own. What Is Dell Doing to Cripple the Performance on These Cards? And seeing how many other parts we doled out money for on this particular server, going back would have proved to be a mess and a half. The Dell R210 is rather limited on what RAID options it will work with.
Most people are recommending that these low end H200/H300 cards be replaced ad hoc with H700 and above level cards, but this wasn't an option for us. After some Googling, I even found sites like this one by Blackhat Research that detailed extensive testing done on these lower end RAID cards proving our suspicions true. The Dell forums had numerous posts like this describing issues with speed, and the fine folks at Spiceworks were seeing the same problems. It seems that we weren't alone in our sluggishness using default settings on the PERC H200 card. Even the SAS cable we used was a brand new Startech mini SAS unit, freshly unwrapped from the factory, and otherwise testing out fine. The hard drives were brand new, along with the RAID card. All of the internal hardware on this server tested out just fine. The problem? After we loaded on a fresh copy of Windows Server 2012 R2, things just seemed strange.
It also doesn't help that the R210 only has a pair of 3.5-inch internal drive bays not the 4-8 hot swap bays we usually have at our disposal on T4xx series Dell servers. Our storage needs for this client were rather low, so employing Windows Storage Spaces was a moot point for this rollout. We paired a dual set of (rather awesome) Seagate 600GB SAS 15K drives together in a RAID 1 for this H200 controller so that we could pass a single volume up to Windows Server 2012 R2. Until SSD prices come down to the cost/GB levels of what SATA or SAS can provide, spinning hard drives will be the cream of the crop for the foreseeable future.Īnd this described the exact situation we were in for this customer Dell R210 rebuild. The advent of SSDs has rendered the need for caching mechanisms almost extinct, but the reality of the situation in the server world is still that spinning disks make up a majority of the current and ongoing new server installations.
Heck, most drives made in the last ten years have some form of dedicated cache space to provide workstations some performance benefits of writing to cache before writing to the disk.
Even lacking a dedicated cache unit on the card, I knew full well that disk drives in a RAID have their own onboard cache that works pretty well on its own. I didn't think going with an H200 for an R210 refurbishment would be the end of world. For the uninitiated, battery backed flash caches on RAID cards allows for near bulletproof data safety in the face of power failure, while increasing performance of RAID arrays considerably. You can dive into the benefits of BBF on this excellent Dell whitepaper. This is clearly denoted on Dell's full PERC rundown site.