On 07/10/2017 09:21 PM, Per Jessen wrote:
John Andersen wrote:
On 07/10/2017 02:43 AM, Per Jessen wrote:
Offloading to hardware is always about speed and less load on the CPU.
And not something you really have to be concerned with any more. When we were doing raid arrays on a 386, sure.
The general principle still holds - not just for RAID, but also for network and iSCSI. My Proliant servers even have a space for a cache card for the hardware assisted 10GigE interfaces. iSCSI is often offloaded to interfaces with dedicated hardware or even dedicated cards.
But unless you are paying BIG bucks for a raid controller, software raid will outperform hardware raid.
There are situations where swraid won't suffice. When you need more than the usual 4-6 drives for instance, you'll need separate controllers anyway.
I would still bet hardware assist is faster for e.g. RAID6, maybe also RAID5.
I have never benchmarked any advantage for hardware raid. Actually I found Linux softraid always faster. I guess that it's the reliability which matters. HW Raid is usually - OS independent, even inclusive remote storage administration, monitoring etc. - certified for (only) certain hard drive models. So that one can be sure that the whole chain (battery backup-ed Cache, HD cache, etc. will survive a power failure without inconsistent file systems. This makes HW raid according to my experience slower and less flexible. If you want reliability you need to have a controller cache with battery/capacitor and turned off HD write cache. If you don't have a battery you have to turn off any HD write cache. In this case SW Raid is probably much slower than HW Raid with reliable cache. cu, Rudi -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org