On Thu, 5 Dec 2002, JUSTIN GERRY wrote: >>> >Well, technically the Promise FastTrak is nothing more than a >standard IDE controller, with software RAID built into the BIOS. >It is not a hardware RAID card. ><< > >I probably should have asked the question here first. > >My misunderstanding stems from the fact that I thought the IDE RAID >card was indeed a TRUE hardware RAID. Now that I know it is nothing but >software, I will use the RedHat based software RAID and rebuild my >server. This is a very wide common misconception that people have. There are essentially 2 types of RAID cards available. 1) True hardware RAID cards which have a processor on board, and usually battery backed NVRAM. They do the RAID computations in the card's hardware itself, and the battery backed NVRAM helps to ensure disk integrity even if the system gets powered down prematurely. When the system becomes powered up again, the card will continue writing to disk the data that didn't get written before the power went out. 2) "Firmware RAID" such as the Promise FastTrak. These cards are software RAID, but the RAID code itself is stored in the ROM chip on the card. The primary use for these cards is when true hardware RAID is too expensive, and your OS of choice does not have built in software RAID capabilities. OS's such as Windows 95/98/ME for example do not have software RAID capability built in. If you want to use RAID, you need to purchase a hardware RAID board, however that can be more cost than is really viable. The firmware RAID cards allow Windows 95/98 users to have RAID capability without spending a fortune. Another usage of firmware RAID is when you would like to dualboot between 2 different OS's and use software RAID with both on the same disks, and the 2 OS's do not natively support a common RAID format. For example sharing a RAID array between Windows and Linux. Many people do not realize the major difference between true hardware RAID cards and these firmware RAID cards however, and purchase the firmware RAID hardware thinking it is hardware RAID with the intent of usage under Linux alone. Unless one is sharing the RAID array with Windows or some other OS like I mentioned above however, there is really no benefit to firmware RAID boards. Linux "md" RAID is vastly superior. In many situations as well, on systems with a very modern high speed processor or processors, Linux "md" RAID is faster than real hardware RAID cards, simply due to the fact that the raw processing power of 2 1.6Ghz CPUs doing software RAID is faster than the piddly 100Mhz or whatever speed dedicated CPU on the hardware RAID cards. Of course Linux software RAID can never give the reliability guarantees that a battery backed NVRAM hardware RAID board can give. One just needs to explore both their performance and reliabiility requirements and choose a solution that best meets the job at hand. >Out of curiosity, has anyone here used the Adaptec 2400A? Is this also >a "software" RAID card? I'm not familiar with that one. I know some of the kernel guys talk about 3ware hardware quite a bit, but I don't know specific model names that are considered good. Just be sure when purchasing *any* RAID card, that it is really a hardware RAID card you are getting if it is a hardware RAID card you are looking for. If the card seems really cheap compared to other RAID cards, it probably is not real hardware RAID. Hope this helps. -- Mike A. Harris ftp://people.redhat.com/mharris OS Systems Engineer - XFree86 maintainer - Red Hat -- Psyche-list mailing list Psyche-list@redhat.com https://listman.redhat.com/mailman/listinfo/psyche-list
