From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stan Hoeppner Subject: Re: raid5 to raid6 - reshape very slow Date: Tue, 29 May 2012 02:21:30 -0500 Message-ID: <4FC478FA.2020100@hardwarefreak.com> References: <4FC41970.5080009@infinitedepth.com.au> <20120529105619.4dd15511@notabene.brown> Reply-To: stan@hardwarefreak.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120529105619.4dd15511@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown Cc: Jonathan Molyneux , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 5/28/2012 7:56 PM, NeilBrown wrote: > On Tue, 29 May 2012 10:33:52 +1000 Jonathan Molyneux > wrote: >> md1 : active raid6 sde1[0] sdb1[6] sdh1[5] sdc1[4] sdg1[3] sdd1[2] sdf1[1] >> 7325679680 blocks super 0.91 level 6, 64k chunk, algorithm 18 >> [7/6] [UUUUUU_] >> [=========>...........] reshape = 47.0% (689413888/1465135936) >> finish=4126.9min speed=3132K/sec > The only thing to do is to wait. This is very much a seek-bound operation > and there is little room for making it go faster. With SSDs you'd see the throughput of this operation increase by 2 orders of magnitude (100x) or more, as SSDs have application level seek latency of ~50-80 microseconds, over 100x lower than rotational drives which are in the 10-30 millisecond range depending on spindle speed. Of course, cost/GB for the same total storage is 2 to 10 times higher with SSD. Though interestingly the price of SSDs continues to fall, whereas the rotational drive manufacturers are currently keeping drive prices artificially high, between 50-100% higher than last year depending on drive model, in an effort to recoup apparent financial losses caused by the flooding in Thailand. -- Stan