i think yes (hd wake up on write/read command) check linear and stripe layout linear is like a lvm (concatenation) i think raid0 work like stripe, but need to check it and return (raid0 = 0 = stripe level, linear!=raid0 for linux implementation) 2011/1/31 Mathias Burén <mathias.buren@xxxxxxxxx>: > On 31 January 2011 21:25, Roberto Spadim <roberto@xxxxxxxxxxxxx> wrote: >> 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 >> > > I meant "default RAID0 setup with mdadm", with a minimum of 2 HDDs, > and any fs on top of that. (with or without lvm) > > Unless the file is very small (smaller than the minimum piece of data > that's being spread across all devices in the RAID0 setup (btw, that's > this called in RAID0, is it chunk size? Stripe size?)) or cached, > you'll wake the HDDs up. Right? > > // Mathias > -- > 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
