From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Fjellstrom Subject: Re: recommended way to add ssd cache to mdraid array Date: Mon, 14 Jan 2013 02:06:05 -0700 Message-ID: <201301140206.05052.thomas@fjellstrom.ca> References: <201212212357.19292.thomas@fjellstrom.ca> <201301111151.44384.thomas@fjellstrom.ca> <24DE0AA3-FAEF-4FF1-BAA5-B3A6B041C2B9@colorremedies.com> Reply-To: thomas@fjellstrom.ca Mime-Version: 1.0 Content-Type: Text/Plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <24DE0AA3-FAEF-4FF1-BAA5-B3A6B041C2B9@colorremedies.com> Sender: linux-raid-owner@vger.kernel.org To: Chris Murphy Cc: linux-raid Raid List-Id: linux-raid.ids On Sun Jan 13, 2013, Chris Murphy wrote: > On Jan 11, 2013, at 11:51 AM, Thomas Fjellstrom =20 wrote: > > On Fri Jan 11, 2013, you wrote: > >> OK fair enough, and as asked earlier, what's the chunk size? > >=20 > > Ah, sorry, I missed that bit. I didn't tweak the chunk size, so I h= ave > > the default 512K. >=20 > OK now that the subject has been sufficiently detoured=85 >=20 > Benchmarking can perhaps help you isolate causes for problems you're > having, but you haven't said what problems you're having. You're usi= ng > benchmarking data to go looking for a problem. This is a GigE network= to > the NAS? If it's wireless, who cares, all of these array numbers are > better than wireless bandwidth and latency. If it's GigE, all of your > sequential read write numbers exceed the bandwidth of wired. So what'= s the > problem? You want better random read writes? Rebuild the array with a= 32KB > or 64KB chunk size, knowing you may take a small hit on the larger > sequential read/writes. I did the "just ignore it" with my last array. This time around I figur= ed it=20 would be a good idea to make sure everything is setup as correctly as i= s=20 possible given the hardware I have, because once its setup, It's too la= te to=20 fix any issues found that need changes to the lower level settings. To me, the write performance shown so far seems quite low, which hints = at a=20 problem that could be solved with some config change before I put it in= to=20 "production". I would like to get it right (as I can), and learn a litt= le in=20 the process. > Chris Murphy-- > 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 http://vger.kernel.org/majordomo-info.html --=20 Thomas Fjellstrom thomas@fjellstrom.ca -- 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