On Sun, Dec 11, 2022 at 09:45:57PM -0500, Alvin Starr via talk wrote: > A raid card can offload some of the overhead that the OS would have to deal > with in terms of co-ordination of multiple writes. > In the case of raid-1 the extra overhead of multiple writes should be > minimal but for raid-4 and above there are a number of data manipulations > that need to be preformed and these will burn up CPU cycles. > > Raid cards often include a battery backed up cache which can significantly > improve disk performance. > The cache also helps with an issue called "write-hole" which can happen in > raid-4,5,6 ( For those with trouble sleeping I suggest > https://lwn.net/Articles/665299/ ). > > Otherwise I do not believe that raid cards have any features that are > unavailable in Linux using the md tools. > > Once again if your running raid of any type make sure you have an automated > check that will test the array health and send out a warning if there is a > problem.
Not sure what the performance is like these days but I certainly remember putting raid cards in IBM servers 15 or 20 years ago, and the performance dropped to 1/3 of what linux could do with software. Sure the cpu load dropped a little bit but it wasn't using that much in the first place. That's before considereing the firmware bugs in the raid controller that allowed you to create volumes over 2TB each, but refused to allow resizing or changing of them afterwards if you did. Software raid is way more flexible, faster, and much easier to change and move to a new machine later. And cheaper too. -- Len Sorensen --- Post to this mailing list [email protected] Unsubscribe from this mailing list https://gtalug.org/mailman/listinfo/talk
