just if you need information on all disks define your read. are you reading 1 byte or many bytes (on all hds?) the number of bytes read/write is the point if you need another disk to read/write you need to wake up your another hd check this implementations on mdadm: linear, raid0, 0, stripe maybe one is better for low power than another, but maybe one is faster than another 2011/1/31 Mathias Burén <mathias.buren@xxxxxxxxx>: > On 31 January 2011 21:09, Roberto Spadim <roberto@xxxxxxxxxxxxx> wrote: >> you psu must be dimensioned to work with everythink at full work load >> (it´s a real production NAS right?! not a test) >> your SAS/IDE/SATA controller and HDD manual should be checked >> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up? >> on linux raid we have a read algorithm and a write algorithm >> if a raid1 write occur all disks will wake up >> if a raid1 (raid0 or another) read occur only the disk will wake up >> >> but check you SATA/IDE/SATA controller, how it wake up your disk, and >> how you hdd wake up >> >> 2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@xxxxxxxx>: >>> Hi all, >>> >>> assuming there is a NAS, with, for example, 10 HDDs >>> in RAID-6. Assuming the HDDs are put in standby, in >>> order to save energy, when the NAS is not used. >>> How is the spin up sequence when the corresponding >>> /dev/mdX device is accessed? >>> Will the system spin up one HDD at time or all together? >>> >>> Obviously, one at time will limit the peak current, >>> thus allowing a better dimensioned PSU, working almost >>> always around the optimal efficiency point. >>> >>> Thanks a lot for any information on the topic, >>> >>> bye, >>> >>> -- >>> >>> piergiorgio >>> -- >>> 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 >> > > I would guess, that on a RAID0 setup, any read to that md device would > wake every disk up in that setup. No? > > // Mathias > > -- 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
