From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roberto Spadim Subject: Re: Adaptive throttling for RAID1 background resync Date: Fri, 18 Mar 2011 17:28:37 -0300 Message-ID: References: <201103181549.20835.xavier@alternatif.org> <10FC03A59E498D4A90A45E4A105AD3ED02EE70F539@EXCH-MBX-2.vmware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <10FC03A59E498D4A90A45E4A105AD3ED02EE70F539@EXCH-MBX-2.vmware.com> Sender: linux-raid-owner@vger.kernel.org To: Hari Subramanian Cc: "linux-raid@vger.kernel.org" List-Id: linux-raid.ids maybe this could be better solved at queue linux kernel area... at elevators or block devices 2011/3/18 Hari Subramanian : > I am hitting an issue when performing RAID1 resync from a replica hos= ted on a fast disk to one on a slow disk. When resync throughput is set= at 20Mbps min and 200Mbps max and we have enough data to resync, I see= the kernel running out of memory quickly (within a minute). From the c= rash dumps, I see that a whole lot (12,000+) of biovec-64s that are act= ive on the slab cache. > > Our guess is that MD is allowing data to be read from the fast disk a= t a frequency much higher than what the slow disk is able to write to. = This continues for a long time (> 1 minute) in an unbounded fashion res= ulting in buildup of IOs that are waiting to be written to the disk. Th= is eventually causes the machine to panic (we have panic on OOM selecte= d) > > From reading the MD and RAID1 resync code, I don't see anything that = would prevent something like this from happening. So, we would like to = implement something to this effect that adaptively throttles the backgr= ound resync. > > Can someone confirm or deny these claims and also the need for a new = solution. Maybe I'm missing something that already exists that would gi= ve me the adaptive throttling. We cannot make do with the static thrott= ling (sync_speed_max and min) since that would be too difficult to get = right for varying IO throughputs form the different RAID1 replicas. > > Thanks > ~ Hari > -- > 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