High-End LSI controllers and the effect of large caches on I/O
On all of my Poweredge machines, I have a 6Gbps 2Tb Samsung EVO 870 as boot drive. They are configured as a single LUN RAID-0. Here's an example with my T140 (sporting an H740P PERC): # megaclisas-status -- Controller information -- -- ID | H/W Model | RAM | Temp | BBU | Firmware c0 | PERC H740P Adapter | 8192MB | 54C | Good | 50.5.1-2818 -- Array information -- -- ID | Type | Size | Strpsz | Flags | DskCache | Status | OS Path | CacheCade |InProgress c0u0 | RAID-0 | 1818G | 512KB | ADRA,WB | Enabled | Optimal | /dev/sda | None |None [....] -- Disk information -- -- ID | Type | Drive Model | Size | Status | Speed | Temp | Slot ID | LSI ID c0u0p0 | SSD | S620NG0R303366N Samsung SSD 870 EVO 2TB SVT02B6Q | 1.818TB | Online, Spun Up | 6.0Gb/s | 38C | [:0] | 0 [....] These drives typically max out unbuffered I/O at around 550MB/s, yet on a freshly booted idl...