--- Molle Bestefich <molle.bestefich@xxxxxxxxx> wrote: > David F. Bakker wrote: > > I have a server with lots of available RAM (10GB) > I > > wanted to create an md raid 1 device that would > mirror > > a large ramdisk (2GB) to a scsi md device. The > > thinking here is writes will be just as fast as > always > > since I/O is sync to both the RAM and hard disk. > > However reads should be crazy fast since it should > be > > coming from the device with the lower latency or > the > > one that answers first (RAM). It looks like the > I/O is > > done in a round robin setup. I get amazing reads > every > > other test (cat'n a file) which seems it is a > round > > robin scheme. Can this be changed somehow to > prefer a > > device or use latency instead? > > Linux should use any available RAM for disk cache. > Are you sure that using MD as a disk cache like > above is any faster than that? > No Im not. I would assume it would be since if I start a large service (1GB) and then stop it and restart it it takes just as long. I was thinking since everything would already be in ram that it would start much faster. However after thinking about this somemore it's probaly the apps internal init that is slow and not the actual executable load time. I did make a change to raid1.c to favor ram disks if present which shows some great read speeds but I havent tested the whole thing out yet. __________________________________ Yahoo! Mail Mobile Take Yahoo! Mail with you! Check email on your mobile phone. http://mobile.yahoo.com/learn/mail - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
