i was trying to search coder for round robin balance, i founded Roy Keene how could we contact him and tell if he could help us? http://www.spinics.net/lists/raid/msg30003.html 2011/2/3 Keld Jørn Simonsen <keld@xxxxxxxxxx>: > On Thu, Feb 03, 2011 at 01:50:49PM -0200, Roberto Spadim wrote: >> hummm, nice >> keld (or anyone), do you know someone (with time, not much, total time >> i think it?s just 2 hours) to try develop modifications on raid1 >> read_balance function? > > maybe our very productive Polish friends at Intel could have a look. > But then again, I am not sure it is productive. I think raid1 is OK, > You could have a look at raid10, where "offset" has been discussed as > being the better layout for ssd. > >> what modification, today read_balance have distance (current_head - >> next_head), multiply it by a number at /sys/block/md0/distance_rate, >> and make add read_size*byte_rate (byte_rate at >> /sys/block/md0/byte_read_rate), with this, the algorithm will make >> minimal time, and not minimal distance >> with this, i can get better read_balance (for ssd) >> for a second time we could implement device queue time to end (i think >> we will work about 1 day to get it working with all device >> schedulers), but it?s not for now > > Hmm, I thought you wanted to write new elevator schedulers? > > best regards > keld > >> >> 2011/2/3 Keld Jørn Simonsen <keld@xxxxxxxxxx>: >> > On Thu, Feb 03, 2011 at 12:35:52PM -0200, Roberto Spadim wrote: >> >> =] i think that we can end discussion and conclude that context (test >> >> / production) allow or don't allow lucky on probability, what's lucky? >> >> for production, lucky = poor disk, for production we don't allow >> >> failed disks, we have smart to predict, and when a disk fail we change >> >> many disks to prevent another disk fail >> >> >> >> could we update our raid wiki with some informations about this discussion? >> > >> > I would like to, but it is a bit complicated. >> > Anyway I think there already is something there on the wiki. >> > And then, for one of the most important raid types in Linux MD, >> > namely raid10, I am not sure what to write. It could be raid1+0, or >> > raid0+1 like, and as far as I kow, it is raid0+1 for F2:-( >> > but I don't know for n2 and o2. >> > >> > The German version on raid at wikipedia has a lot of info on probability >> > http://de.wikipedia.org/wiki/RAID - but it is wrong a number of places. >> > I have tried to correct it, but the German version is moderated, and >> > they don't know what they are writing about. > > at least in some places, refusing to correct errors. > >> > http://de.wikipedia.org/wiki/RAID >> > >> > Best regards >> > Keld >> > >> >> 2011/2/3 Drew <drew.kay@xxxxxxxxx>: >> >> >> for test, raid1 and after raid0 have better probability to don't stop >> >> >> raid10, but it's a probability... don't believe in lucky, since it's >> >> >> just for test, not production, it doesn't matter... >> >> >> >> >> >> what i whould implement? for production? anyone, if a disk fail, all >> >> >> array should be replaced (if without money replace disk with small >> >> >> life) >> >> > >> >> > A lot of this discussion about failure rates and probabilities is >> >> > academic. There are assumptions about each disk having it's own >> >> > independent failure probability, which if that can not be predicted >> >> > must be assumed to be 50%. At the end of the day I agree that when >> >> > the first disk fails the RAID is degraded and one *must* take steps to >> >> > remedy that. This discussion is more about why RAID 10 (1+0) is better >> >> > then 0+1. >> >> > >> >> > On our production systems we work with our vendor to ensure the >> >> > individual drives we get aren't from the same batch/production run, >> >> > thereby mitigating some issues around flaws in specific batches. We >> >> > keep spare drives on hand for all three RAID arrays, so as to minimize >> >> > the time we're operating in a degraded state. All data on RAID arrays >> >> > is backed up nightly to storage which is then mirrored off-site. >> >> > >> >> > At the end of the day our decision around what RAID type (10/5/6) to >> >> > use was based on a balance between performance, safety, & capacity >> >> > then on specific failure criteria. RAID 10 backs the iSCSI LUN that >> >> > our VMware cluster uses for the individual OSes, and the data >> >> > partition for the accounting database server. RAID 5 backs the >> >> > partitions we store user data one. And RAID 6 backs the NASes we use >> >> > for our backup system. >> >> > >> >> > RAID 10 was chosen for performance reasons. It doesn't have to >> >> > calculate parity on every write so for the OS & database, which do a >> >> > lot of small reads & writes, it's faster. For user disks we went with >> >> > RAID 5 because we get more space in the array at a small performance >> >> > penalty, which is fine as the users have to access the file server >> >> > over the LAN and the bottle neck is the pipe between the switch & the >> >> > VM, not between the iSCSI SAN & the server. For backups we went with >> >> > RAID 6 because the performance & storage penalties for the array were >> >> > outweighed by the need for maximum safety. >> >> > >> >> > >> >> > >> >> > -- >> >> > Drew >> >> > >> >> > "Nothing in life is to be feared. It is only to be understood." >> >> > --Marie Curie >> >> > >> >> > >> >> >> >> >> >> >> >> -- >> >> Roberto Spadim >> >> Spadim Technology / SPAEmpresarial >> >> -- >> >> 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 >> > -- >> > 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 >> Spadim Technology / SPAEmpresarial > -- > 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 Spadim Technology / SPAEmpresarial -- 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
