From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roberto Spadim Subject: Re: RAID HDDs spin up sequence Date: Mon, 31 Jan 2011 19:35:29 -0200 Message-ID: References: <20110131201823.GA15704@lazy.lzy> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: =?ISO-8859-1?Q?Mathias_Bur=E9n?= Cc: Piergiorgio Sartor , linux-raid@vger.kernel.org List-Id: linux-raid.ids 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 =3D 0 =3D stripe level, linear!=3Draid0 for linux implementation) 2011/1/31 Mathias Bur=E9n : > On 31 January 2011 21:25, Roberto Spadim wrot= e: >> 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 anot= her 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 Bur=E9n : >>> On 31 January 2011 21:09, Roberto Spadim wr= ote: >>>> you psu must be dimensioned to work with everythink at full work l= oad >>>> (it=B4s 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 channe= l 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 u= p >>>> >>>> but check you SATA/IDE/SATA controller, how it wake up your disk, = and >>>> how you hdd wake up >>>> >>>> 2011/1/31 Piergiorgio Sartor : >>>>> 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-r= aid" in >>>>> the body of a message to majordomo@vger.kernel.org >>>>> More majordomo info at =A0http://vger.kernel.org/majordomo-info.h= tml >>>>> >>>> >>>> >>>> >>>> -- >>>> Roberto Spadim >>>> Spadim Technology / SPAEmpresarial >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-ra= id" in >>>> the body of a message to majordomo@vger.kernel.org >>>> More majordomo info at =A0http://vger.kernel.org/majordomo-info.ht= ml >>>> >>> >>> I would guess, that on a RAID0 setup, any read to that md device wo= uld >>> 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@vger.kernel.org > More majordomo info at =A0http://vger.kernel.org/majordomo-info.html > --=20 Roberto Spadim Spadim Technology / SPAEmpresarial -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html