John Andersen wrote:
On 9/11/2014 12:47 PM, Linda Walsh wrote:
It is a solution you get w/o paying extra for a RAID card but that has *no hardware acceleration*... but the BIOS presents a RAID0 or RAID1 set as 1 disk for normal interactions.
I believe you will find the hardware acceleration is mythical anyway. At least that's been my finding.
---- Compare RAID 5, 6, 50, 60 against the same using linux mdraid setups. Check your throughput as well as cpu usage. I think you'll find the mdraid version notably more taxing on your cpu. Of course on RAID0/1/10 no cpu is needed to schedule 2 async writes to each mirror and wait for them to complete. Modern I/O controllers don't write synchronously to single disks, why would they do so to mirrors? Again, John Andersen wrote:
There is one area that you have to be aware of if you put /boot on a mirrored (raid1) drive, the system will always boot from which ever disk your menu.lst says to boot from even if that is part of a MD raid. If that disk fails you have to manually switch your menu.lst to the other. (This is why I avoid /boot on MD raid.)
---- vs. using SW-BIOS RAID, you only see 1 disk for the RAID, you don't see the separate pieces -- not at boot and and not in /dev.
I've had several fake raid cards and several fake raid mother boards, and each time, I did around to find the jumper that disables the fake raid and just use the controllers as separate channels. (The cheapest of the cheap fake raid cards also fake using multiple channels, so buyer beware, your WRITES will be done serially, not in parallel on these cheap cards.).
---- If you say so... but SATA only talks to 1 disk/channel unless you use a SATA multiplexor -- which requires special drivers to work on windows and on linux -- (unlike the SAS expanders, the SATA expanders are cautioned against).
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