at raid1.c there´s a example with ssd and hd with different speeds 2011/2/15 Roberto Spadim <roberto@xxxxxxxxxxxxx>: > writes will be the speed of slowest mirror (ssd or hd) > read can have speed improvement with this patch > > there´s some options > > /sys/block/md0/md/read_balance_mode > > near_head = today implementation > round_robin => could be usefull if you have ssd only, since > round_robin consider that access time is the same for any drive (hard > disk access time is diferent for random and sequencial) > stripe => i didn´t get good benchmarks, but it´s nice to have it, > since we could put it over network, some sectors on one disk others on > another (nbd) > time_based => here you should send me some information about you disk > for example: > access time of mirrors (check your drive information website, ssd > are normaly <0.1ms, hard disks near 10~20 ms) > sequencial read speed (use dd if=/dev/sda of=/dev/zero bs=4096, > change the block size to size you will use with your filesystem, for > vertex2 ssd i´m using bs=4096, for disks it´s a good value too, since > disks bs ~= number of heads (2,4,8) ) > > send me the access time and sequencial read speed and i make the > values to tune your sysfs (/sys/block/md0/md/read_balance_config) > > you will need to : > > echo "time_based" > /sys/block/md0/md/read_balance_mode > echo "disks informations" > /sys/block/md0/md/read_balance_config > > for each mirror, you can´t use sysfs file to configure it, maybe a > bash script is a better solution to configure it, on future version i > will change it and put at /sys/block/md0/md/dev-xxxx/ > > 2011/2/15 Andras Korn <korn@xxxxxxxxxxxxxxxxxxxxxxx>: >> On Tue, Feb 15, 2011 at 06:10:17AM -0300, Roberto Spadim wrote: >> >>> andras could you make some benchmarks to raid1 with round robin read balance? >>> at this site: >>> www.spadim.com.br/raid1/ >>> >>> it's kernel 2.6.37 based >> >> Yes, I can do that. Can you give me some hints on what specific >> configuration to try? I see you have some sysfs tunables. My raid1 array >> consists of two spinning disks and an SSD, all local. >> >> Do you expect this patch to make a difference in my case? With the spinning >> disks marked as write-mostly, I'm getting close to the read performance of >> the SSD (except for very small random reads, for some reason). >> >> It's random writes that are much slower than with only the SSD. >> >> -- >> Andras Korn <korn at elan.rulez.org> >> There is no spoon(). But there is a fork(). >> -- >> 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 > -- 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
