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: Mon, 28 May 2012 14:05:05 +1000 Message-ID: <20120528140505.6eb49b26@notabene.brown> References: <4FBA0047.5050208@profitbricks.com> <20120522092817.1b5946b8@notabene.brown> <4FBF7CAD.7000307@profitbricks.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/Yr1l4uVldO1jvEktQb+tuJ9"; protocol="application/pgp-signature" Return-path: In-Reply-To: <4FBF7CAD.7000307@profitbricks.com> Sender: linux-raid-owner@vger.kernel.org To: Sebastian Riemer Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/Yr1l4uVldO1jvEktQb+tuJ9 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Fri, 25 May 2012 14:35:57 +0200 Sebastian Riemer wrote: > Hi Neil, >=20 > On 22/05/12 01:28, NeilBrown wrote: > >=20 > > This should be fixed in linux 3.4 with commit 6b740b8d79252f13bcb7e5d3c= 1d > >=20 >=20 > I've tested the RAID 01 with kernel 3.4 and it isn't fixed. It is even > worse, because direct IO doesn't work any more on the raid1 device (with > kernel 3.2 it worked). What do you mean by "doesn't work"? Returns errors? crashes? hangs? kills you cat? It works for me. When I use 32K direct writes to a RAID1, both underlying RAID0 arrays see 64-sector writes. (when I do normal buffered writes I see 8-sector writes which seems odd, but clearly md/RAID1 is allowing large writes through) NeilBrown >=20 > There are still 4k chunks which aren't merged in the raid0 devices below > (blkparse -i md100 -i md200 -i md300 | less). > Could you also check this on your setup, please? >=20 > Cheers, > Sebastian >=20 >=20 > Btw. this is my test script: >=20 > #!/bin/bash > if [ "`lsmod | grep brd`" =3D=3D "" ]; then > modprobe brd rd_nr=3D4 rd_size=3D524288 > fi > mdadm -C /dev/md100 --force --assume-clean -n 2 -l raid0 /dev/ram0 /dev/r= am1 > mdadm -C /dev/md200 --force --assume-clean -n 2 -l raid0 /dev/ram2 /dev/r= am3 > blktrace /dev/md100 & > pid=3D$! > dd if=3D/dev/zero of=3D/dev/md100 bs=3D1M oflag=3Ddirect > kill -2 $pid > blktrace /dev/md200 & > pid=3D$! > dd if=3D/dev/zero of=3D/dev/md200 bs=3D1M oflag=3Ddirect > kill -2 $pid > mv md100* r0_only/ > mv md200* r0_only/ >=20 > mdadm -C /dev/md300 --force --assume-clean -n 2 -l raid1 /dev/md100 > /dev/md200 > blktrace -d /dev/md100 -d /dev/md200 -d /dev/md300 -b 4096 & > pid=3D$! > # Kernel 3.4 doesn't support direct IO on the md300 device > dd if=3D/dev/zero of=3D/dev/md300 bs=3D1M > kill -2 $pid > -- > 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 --Sig_/Yr1l4uVldO1jvEktQb+tuJ9 Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBT8L5cTnsnt1WYoG5AQJYfg//ffqhxaUlsN3Nd+dTP9ZmsdBtSlOgDgwk 15j0rHtyPnNH4FJJ/WEXQkpQf+4ljFl1lCMZALp8f7dsgwvgZn8TOGzjuHGDzSEa LKX1ysxtuuAiRHAftq6Z6Hz0pTIg0Jg42TYnTQvwDm/zDN6gGbr9NwDurIOzkp+A Q2r7p8uX7xtQ/DD5zlgUWsosj6b1ly3niJu0bgT4RTb7FEYGq/xEnjJbsuXKEbbG mL0Afpevu5NhdHKbCWMEB3WQe+XgKiRE7YmIt6S0qnAZc/+vG32mgyj38HhVQZ0C vOFMX/VJitBDsRf3hbueiHGlnQr+tCfP8gmJZubfeBlGTXPmpafhSLOVW/OMeDwi myLaxUwYkFrOymo9AgQVQ/QkOny9ScSIdffulkuWGzaxhon+YD3gO4yTFRRrj2jK QJZxqP36XSiAsEM8JoLoWOEJn0BkjUhHipjSeBa3b4NzgGqFLRECUEYgRiUsaSJm GAwG1iecU0QNfcnsJ79oi3z6ntu+Hto9TYaIzETM8xDZ7xADLAMGB6orRBTUMYDa dsUjGJJ/mlOrJeF7hYbVF93IwF9MgxxyaEnT4AHsyuWvXCbqRBYvNXT2OnOQY8eD rqC1Lry3HdzLr1zUvoOFbhPQeFv/m7vhJRdyQIUVC0Mh6M1HAfDtFDC0vwS/vTTV UePB4Csf0u0= =jDRf -----END PGP SIGNATURE----- --Sig_/Yr1l4uVldO1jvEktQb+tuJ9--