From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: Speeding up reading with RAID1 and --write-mostly Date: Mon, 15 Sep 2014 14:11:33 +1000 Message-ID: <20140915141133.0a4da9ad@notabene.brown> References: <20140913060143.GA15849@fishbowl.rw.madduck.net> <20140913162301.GB14969@fishbowl.rw.madduck.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/+895=fZ5o1Ilp.B.z8G0xp0"; protocol="application/pgp-signature" Return-path: In-Reply-To: <20140913162301.GB14969@fishbowl.rw.madduck.net> Sender: linux-raid-owner@vger.kernel.org To: martin f krafft Cc: "linux-raid@vger.kernel.org" List-Id: linux-raid.ids --Sig_/+895=fZ5o1Ilp.B.z8G0xp0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Sat, 13 Sep 2014 18:23:01 +0200 martin f krafft wrote: > also sprach Roberto Spadim [2014-09-13 13:56 +020= 0]: > > Try a bcache or something like it >=20 > The problem with a cache is that the data have to be read once from > the slow disk anyway, whereas I am proposing to keep a shadow copy > on rotational disk, really, just in case the MMC may need to be > removed at some point. >=20 It is a persistent cache though. So it only needs to be read once. If the cache SD is the same sizes as the main device then it should never ever need to read again. But I suspect you will find that SD cards aren't really fast enough for your needs. It wouldn't hurt to experiment on just an SD card and see how it performs. NeilBrown --Sig_/+895=fZ5o1Ilp.B.z8G0xp0 Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIVAwUBVBZm9Tnsnt1WYoG5AQK1XxAAurFNdP2lgdwwtzqOmkvs8n5EGzZ95Aa+ H9Iuw9TTkPg7yXxVKvagRMU+fA4zO9azYMqQ0I3iTHH9wTTMonYyXCPgOaKMoBFx ZlHKSRxFT7+uBHUvsVqiSic3ALvW+MAavmE4C2XlJqH+9cThdBlPxX8eWuT7Vkrs MIfKdXkthFGgd0wLI9U+68kpN821gLNNimx8Snd6HYq1uvuBDpGoKLPnyoumoqbD I96sFJncxjueNv2kO+ta59lde7z/Ii1ZH4comoRStoi5al6Wj7gkR7CSpXnCmjUV 53c3qPEyzO2dsre1c7i/xesSZuEQDfDWjGCLevt7AjNvU328dzMTBwptz895qY+C 1DwMdItnO5rpSzPnbXkIBroGIGANlh1vuelj50A9P8sbwtqASHwMD86mUpzyHF08 KeBYZLLFE4p38rXO2cuVmCKurhUeVFbKRajnL7HzpY/6/dxgYvbhDhXzJLtaR5t5 gGt7XwmTYEUg1ACNDze7ICD7QNUGZU76X5t4a6Gy6z6S9FfU2jzrceYcGkpnk9Zb Lueji2mJOoqwNuTTQ2JAQUB+giJX6qEC3bNU+aLRMqWc7QBUOcFR4N0AgNaHp+ji k49XSOjfLoEF83Zwhc5SDdApW8cwDARyVnixxSP5TAtbTQufF0xugUl7DOVwJ7ez /vUESYpFNk0= =Ee05 -----END PGP SIGNATURE----- --Sig_/+895=fZ5o1Ilp.B.z8G0xp0--