very nice i think that bcache is the solution another question (ok i know...) could we improve read/write performace on raid1 for ssd? round robin is better than near head (since ssd don´t have head) i think there´s a patch for it just test it and put at linux kernel (ok it will have a time to be on stable linux kernel) thanks neil! 2011/1/19 Roberto Spadim <roberto@xxxxxxxxxxxxx>: > there´s a forum (linux kernel) for ideas? > > 2011/1/19 NeilBrown <neilb@xxxxxxx>: >> On Wed, 19 Jan 2011 18:13:23 -0200 Roberto Spadim <roberto@xxxxxxxxxxxxx> >> wrote: >> >>> Hi guys, from a long email i will start this one: (the last one wasn´t send) >>> >>> think about this: >>> >>> /dev/sda (sata disk 1000gb size, latency of 1ms to move head, 100mb/s >>> to write/read) >>> /dev/sdb (ssd 1gb size, latency of <100us to find what flash and >>> position, 500mb/s to write/read) >>> ram memory (8gb size, with 1gb not used) >>> /dev/mdxxx (the new device i´m calling it as raid0-cache) >>> >>> how raid0-cache work? >>> >>> >>> how to create raid? >>> tell what the sequencial read cache estrategy: >>> memory(tell fixed memory size) - /dev/sdb - /dev/sda - another device >>> (maybe just 2 is suficiente /dev/sdb and /dev/sda)... >>> >>> >>> how to read? >>> first, read from the first read device (memory) >>> if information not there -> read from second read device (/dev/sdb), >>> update information at first read device, return the read value >>> if information not there -> read from third read device (/dev/sda), >>> update information at second and first read device, return the read >>> value >>> >>> how to write? >>> flush space from first read device to second read device >>> write to first read device, return OK >>> >>> background thread: >>> sync from first write device (memory) to second write device (/dev/sdb) >>> flush from second write device (/dev/sdb) to third write device (/dev/sda) >>> >>> startup: >>> using cache: >>> flush everythink from first write device (memory) to second write >>> device (/dev/sdb) >>> flush everythink from second write device (/dev/sdb) to second write >>> device (/dev/sda) >>> since memory is volatille, at startup it can´be flushed... >>> without cache: >>> make first write device unusable (memory) >>> make second write device unusable >>> here we can have write problems, since a wrong power off, can lost >>> information from cache (first and second write device) >>> >>> >>> >>> anyidea who can make it? >> >> "Hey, I've got this clever idea, I wish someone would implement it" almost >> always results in ... nothing. >> People with the ability to implement are much more interested in implementing >> their own ideas. >> >> But see also "bcache". >> >> NeilBrown >> >>> thanks >>> -- >>> 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 > -- 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
