Hi guys, i done some tests some time ago, and what i can tell is Raid1 use the nearest disk algorithm to select what disk will execute reads (read balance) i think it's very good, but don't consider diferent disk speed (access time and continous read), but it do a very good job i don't know there's space to improvement here, i got 1% of speed up doing a mix of disk speed (7.2k rpm 5k rpm and 15k rpm and a ssd) and changing the read balance algorithm i think it's solid 1% of speed up, but confuse to config parameters, parameters are based with access time (head time to move from position 0 to end of disk, or 0 for ssd) and continous read (based on mb/second in a continous read, or based on rpm and track size) the best i got is: if you want raid1 you will run a system like databases, or multi thread systems, each thread operating a disk if have a system with continous read/write (dvr, stream, etc) raid10 far is the best maybe more tunes you can do with align, read ahead, and others filesystem options/parameters and cache, a raid card with flash backup or battery is nice too good luck 2014/1/24 <keld@xxxxxxxxxx> > > On Fri, Jan 24, 2014 at 08:56:02AM -0600, Matt Garman wrote: > > On Fri, Jan 24, 2014 at 6:04 AM, <keld@xxxxxxxxxx> wrote: > > > The reading is not balanced because it does not make sense to do balanced > > > reads for sequential reading. In RAID-1 the disk sectors are consequitive. > > > So if you would read one sector from one disk, and the following sector from the other disk, > > > then the next read from disk 1 would need to skip a full resolvation of the disk, > > > which may cost something like 8 ms. So better read contigously from the same disk, and hope > > > for some other IO request that can use disk 2. > > > > > > Does that rationale hold for SSDs? > > No, this is not relevant for SSDs as access time is almost zero. > > best regards > keld > -- > 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 -- Roberto Spadim -- 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
