From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: Reason for md raid 01 blksize limited to 4 KiB? Date: Tue, 29 May 2012 20:25:59 +1000 Message-ID: <20120529202559.6aa7fd49@notabene.brown> References: <4FBA0047.5050208@profitbricks.com> <20120522092817.1b5946b8@notabene.brown> <4FBF7CAD.7000307@profitbricks.com> <20120528140505.6eb49b26@notabene.brown> <4FC49733.9050905@profitbricks.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/dXcR_WiMuKUQeuGCIvu4USC"; protocol="application/pgp-signature" Return-path: In-Reply-To: <4FC49733.9050905@profitbricks.com> Sender: linux-raid-owner@vger.kernel.org To: Sebastian Riemer Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/dXcR_WiMuKUQeuGCIvu4USC Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 29 May 2012 11:30:27 +0200 Sebastian Riemer wrote: > On 28/05/12 06:05, NeilBrown wrote: > > What do you mean by "doesn't work"? Returns errors? crashes? hangs? ki= lls > > you cat? > >=20 >=20 > dd with oflag=3Ddirect returned an IO error. Odd. Updating mdadm shouldn't affect that. >=20 > > It works for me. > >=20 > > When I use 32K direct writes to a RAID1, both underlying RAID0 arrays s= ee > > 64-sector writes. > >=20 > > (when I do normal buffered writes I see 8-sector writes which seems odd, > > but clearly md/RAID1 is allowing large writes through) > >=20 >=20 > Now, I've updated mdadm to version 3.2.5 and it works like you've > described it. Thanks for your help! But the buffered IO is what matters. > 4k isn't enough there. Please inform me about changes which increase the > size in buffered IO. I'll have a look at this, too. I don't know. I'd have to dive into the code and look around and put a few printks in to see what is happening. NeilBrown --Sig_/dXcR_WiMuKUQeuGCIvu4USC Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBT8SkNznsnt1WYoG5AQKxsxAAlJ5eeTo/cYmoXOYjNu3Iwdcs9lG/ZFOR qVTcN0+GEl6TG9U8Bye4+WDv6fz/JMMWtF9XbY7hWNVx0Js/tbGZDA3w0LsCTaoi RDsLAUqmImX22eJ8XaQNKyrk3F2WcgEgD1sZ3oG51ZgDmKA1lDdd5LMTmv6bx/Lk QOelimqDrIldM8AiWJG5wPasDaaamsRI2+ORAAg1fe6mTLEeCVyl6Zt88OzxnXUw loZZAN0VVY4dV4/+yXupG3UAp45/dnFuqt5Oi5s5hm3tbnVzL5+poGCegzGGYOvL 6wN6dWCAfhno7ypAQ3cvLxHqxoeoEqGxzHoLXwdB2DSeLKJcKKJtE15ec9+xAyGA 1T0PWZw2TRVY3NtiSbBwBW6WQ8uHlviDREMZdtxR3tsl1oQjF05l8p5ngW8zkOYY qJS71q/UZwhdYiZv1O7TFTSK3BLkMzY/fpTPzh+0HqvwvnUAiqkbzhD7ZN+rLKt8 MOU6tah4S4kCsYU7cbireQ0ZFmBaooOwEy3Urr/1XIKzQsshUgVxJxyRv2jpF+2a M/lgEAFV3pfTO5NNGUeV9Fm7pQyJgydR0insoolehuFjb253PHOdcoxv/jZQmj3n L++hkOlmun/7q9KB3BZNS9rm0XPiQiNu1/qUrw/m+HVAPZoD2TQT/wjAsfBhXWCs kkVIWwzHGRU= =p5gE -----END PGP SIGNATURE----- --Sig_/dXcR_WiMuKUQeuGCIvu4USC--