maybe it´s the intention of 'mcachefs' http://sourceforge.net/apps/mediawiki/fuse/index.php?title=FileSystems 2011/1/19 Roberto Spadim <roberto@xxxxxxxxxxxxx>: > hummm.... > thinking again..... > > what´s the today raid1 problem? > it´s based on minimal disk size > for example... > /dev/sda 1gb > /dev/sdb 1tb > we can have a 1gb raid only > > what you want is: > 1tb raid0 > with a automatic /dev/sda to /dev/sdb write > > > could we call this raid0-cache? > i think we could implement it in raid.... > > check this fuse (filesystem) implementation: http://www.furquim.org/chironfs/ > it´s based on filesystem (ok it´s a raid1, not a cache like, but´s > limited to max filesystem size, not the minimal filesystem size... ok > it´s not secure to use it since small filesystem don´t have all > information, but´s nice) > > anyone want to make raid0-cache implementation? > > > 2011/1/19 Roberto Spadim <roberto@xxxxxxxxxxxxx>: >> i think we could make it >> but not a raid feature >> a linux feature >> for example >> >> we could get ramdisk, nbd (network block device), ssd, hd, scsi, raid >> and select what is first cache, and what is real value >> >> after this device is created we could use it with raid... >> >> >> but.... the problem persist >> if we lost energy, we can´t confirm that ram memory is sync to disk, >> just if we don´t use memory cache... in other words we will work with >> the best cache disk speed) >> >> since ram can get 32GB on big home computer >> and ssd can get 1terabyte on big home computer >> and hdd can get more than 1terabyte on big home computer >> >> we just need time to sync 32GB from memory to ssd >> what´s the ssd speed? 300mb/s? we need 106,6666666666667 seconds to >> sync memory to ssd, can you buy a ups with 107 seconds of life with a >> serial cable (usb maybe) that inform that we are without energy? >> >> >> >> >> >> 2011/1/19 Cory Coager <ccoager@xxxxxxxxx>: >>> On Wed, Jan 19, 2011 at 02:44:31PM -0200, Roberto Spadim wrote: >>>> yes, a jornaling but using ssd first and sata after >>>> it?s not raid feature... >>>> it?s per disk filesystem feature... >>>> we could implement jornaling in raid too... >>>> but?s more inteligent (easy) at application level (filesystem) >>>> you could write first at network (if it?s faster than sata) and after >>>> at sata (if it?s slower than network) >>>> >>>> it?s not a raid feature... it?s a per device feature got it? >>>> maybe a device (not raid..) for a cache division on devices >>>> for example >>>> >>>> >>>> /dev/sda (sata 1terabyte 100mb/s) >>>> /dev/sdb (ssd 1gigabyte 1000mb/s) >>>> >>>> /dev/cache_a (a mix of sata and ssd with sata size 1terabyte, and >>>> mixed speed (memory, ssd, sata)) >>>> >>>> cache_a device should know that >>>> early reads/write should be writen to sdb >>>> time in time it should sync at sda >>>> >>>> the same happens with memory (ram memory) but it?s volatille (diferent >>>> than ssd that?s not volatille) >>>> >>>> /dev/sdb should be sync >>>> /dev/sda should be async (since /dev/sdb make it safe to use async) >>>> >>>> >>>> that?s you intention? i don?t know if linux have it, anyone know? >>> I would use a physical ramdisk over a ssd but thats besides the point. >>> They are still disk drives to the OS. >>> >>> Yes, I guess it would be similar to journaling but done in RAID >>> itself. I don't believe it exists yet, thats why I'm asking if >>> we could add support for this? >>> -- >>> 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 > -- 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
