Ok, So reading out TWO streams serial from each disk would give the speedup, wouldn't it? The driver would just have to cache the four(6,8,..) streams until they are merged? So the driver has just to cache two streams per disk and all would be perfect...? Just as proposal for the future md-raid-driver releases ;)) Florian > -----Ursprüngliche Nachricht----- > Von: Mario 'BitKoenig' Holbe [mailto:Mario.Holbe@xxxxxxxxxxxxx] > Gesendet: Montag, 13. August 2007 16:50 > An: linux-raid@xxxxxxxxxxxxxxx > Betreff: Re: Mustn't be RAID 1 and 0 read-performance be similar? > > Rustedt, Florian <florian.rustedt@xxxxxxxxxxx> wrote: > > If the speed on RAID 0 is based on reading out in parallel, then it > > must be the same on RAID 1, mustn't it? > > On RAID 1, it is possible, to read two blocks in parallel > to speed up, too. > > It's not that simple. > On RAID0 you can read one single stream of data from all of > the disks in > parallel: you read one stream from each disk with each stream > containing completely different data and merge them together > to get the original stream. On RAID1 you can only read > exactly the same stream from all of the disks. Thus, RAID1 > cannot provide RAID0's speed-up for a single stream. > However, if you read multiple streams parallel, RAID1 can do > better than RAID0 because you can read stream1 from disk1, > stream2 from disk2 etc. > Using RAID0, this speed-up can only be achieved for streams > <= chunk size. > > > regards > Mario ********************************************************************************************** IMPORTANT: The contents of this email and any attachments are confidential. They are intended for the named recipient(s) only. If you have received this email in error, please notify the system manager or the sender immediately and do not disclose the contents to anyone or make copies thereof. *** eSafe scanned this email for viruses, vandals, and malicious content. *** ********************************************************************************************** - 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
