On Tue, Oct 14, 2003 at 12:12:33AM +0200, Hermann Himmelbauer wrote: > Hi, > I am considering putting my Swap on a RAID1. > > I am aware that using 2 seperate Swap-Spaces without RAID would > probably speed things up as Linux distributes the swap. Actually the swap-out will be slightly SLOWER, than without RAID-1. However I do use RAID-1 setup extensively in my machines even with this slow-down of writing to disks (must write to two disks!). I want to have the added RELIABILITY benefit. > But what happens if a disk fails and the swap is on this disk? > I assume Linux would crash? Wouldn't a swap on a RAID prevent > such a crash? You will see messages telling that MDnn carrying your swap has failed to write to one of the disks, and is now running in degraded mode. The system will continue to function just fine. (Until your last RAID-1 sub-disk fails ...) Actually I tested that "fail a disk -> observe RAID-1 manage it" just the other day at one machine I am builting presently. As important as having runtime reliability, I consider bootup reliability. Standard bios bootup picks up a disk (or fails), which can suck major way. On a hunch (reading kernel driver sources) I did buy HighPoint RocketRaid card (RR-1520 to be precise), which actually is _software_raid_, e.g. it is simple two channel Serial-ATA interface, but with BIOS understanding its own RAID-labels, and knowing which disks form my bootable RAID-1. The HighPoint allows machine to boot with degraded disks, however it does that by demanding operator intervention, which I am not entirely happy with when considering systems running at remote sites doing their things... (Compare with Sun SPARCs booting autonomously.) Oh yes. I didn't use HPTRAID as it is in 2.4.22 kernel, as that doesn't have code to handle disk offlineness. I allocated lowest cylinder for HPT BIOS raid label (actually that is mere 512 byte block, not needing a megabyte or whatever my "cylinder" became), and then placed usual auto-detect RAID (partition type FD) slices on the rest of the disk, bound slices in between two disks with RAID-1 to become my /boot, swap, and root. > Best Regards, > Hermann > -- > x1@aon.at /Matti Aarnio - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
