From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jack Wang Subject: Re: RAID5 created by 8 disks works with xfs Date: Mon, 2 Apr 2012 18:01:55 +0800 Message-ID: References: <4F776492.4070600@hardwarefreak.com> <4F77D0B2.8000809@hardwarefreak.com> <4F77EA55.6090004@hardwarefreak.com> <4F784A06.1@anonymous.org.uk> <4F795CE2.9050106@anonymous.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <4F795CE2.9050106@anonymous.org.uk> Sender: linux-raid-owner@vger.kernel.org To: John Robinson Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids 2012/4/2 John Robinson > > On 02/04/2012 04:15, Jack Wang wrote: >> >> 2012/4/1 John Robinson > > > > [...] >> >> =C2=A0 =C2=A0Now that you've suggested that, it occurs to me that fo= r an >> =C2=A0 =C2=A0application like this, the OP might be better doing his= multiple >> =C2=A0 =C2=A0slow streams to a spool folder on SSD, and copying over= to the big >> =C2=A0 =C2=A0array of spinning rust when each stream completes. 200 = streams of >> =C2=A0 =C2=A0500MB is 100GB of data, so a pair of slightly larger SS= Ds in RAID1 >> =C2=A0 =C2=A0(or RAID10, to balance the reads coming off) would do n= icely as a >> =C2=A0 =C2=A0spool area. >> >> =C2=A0 =C2=A0This might also be a good application for bcache, Flash= Cache or >> =C2=A0 =C2=A0whatever. >> >> Using bcache/flashcache is what I'm considering, does above >> configuration option still needed? > > > Using a pair of SSDs? I think if you're adding a cache to a redundant= array, you ought to make the cache redundant too. > > Using RAID10 to balance reads coming off the redundant pair of SSDs? = That would depend on how bcache or flashcache is written; if it's singl= e-threaded or does large copies from cache to the backing, then yes, yo= u may see better performance or at least more balanced usage of the two= SSDs, and surely won't see worse performance. > > Cheers, > > John. John, Thanks for reply=C2=A0, I mean using SSD as cache device, and raid5 16*7200rpm disks, is this works for streaming workload above? I know bcache is try to turn rand write to seqencial write, but most ssd is not good at RAND write as I know. Cheers, Jack -- 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