From: Daniel Pocock <daniel@pocock.com.au>
To: Martin Mokrejs <mmokrejs@fold.natur.cuni.cz>
Cc: linux-ide@vger.kernel.org
Subject: Re: very slow write to AHCI device
Date: Mon, 07 May 2012 20:11:51 +0200 [thread overview]
Message-ID: <4FA81067.80607@pocock.com.au> (raw)
In-Reply-To: <4FA81009.1030308@fold.natur.cuni.cz>
On 07/05/12 20:10, Martin Mokrejs wrote:
> Hi Daniel,
>
> Daniel Pocock wrote:
>
>>
>> Hi,
>>
>> I'm testing a problem with the following combination:
>> - SB700/SB800 type controller in AHCI mode (in a HP Microserver N36L)
>> - Seagate Barracuda 1TB 7k2 drive with NCQ
>>
> Is that a disk with 4k hardware sectors (Advanced Format)? Where does
> you partition start? At sector 63 or 2048? ;-)
>
>
At 2048:
Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x484d5754
Device Boot Start End Blocks Id System
/dev/sdb1 * 2048 499711 248832 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sdb2 499712 1953523711 976512000 fd Linux raid
autodetect
>> I've got a fresh 256MB partition, formatted ext4, mounted
>> barrier=1,data=ordered, write-cache enabled (hdparm -W 1 /dev/sdb) and
>> shared over NFS.
>>
>> When the NFS client writes,
>> - unpacking a source tarball, many small files, iostat reports speeds
>> under 500kBytes/sec
>> - dd conv=fsync, iostat reports about 50MB/sec
>>
>> If I set up a USB disk on the same box, with a partition formatted
>> exactly the same way, the iostat reports the write speed (unpacking the
>> same tarball) is over 5MBytes/sec - not so fast, but 10 times faster
>> than the AHCI device.
>>
> So USB is at speed 10 times less, right?
>
>
No - the USB is 10x faster, 5MBytes/sec, the SATA disk is giving me
barely 500kBytes/sec for the same write over NFS
> Martin
> --
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next prev parent reply other threads:[~2012-05-07 18:12 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-07 16:16 very slow write to AHCI device Daniel Pocock
2012-05-07 18:10 ` Martin Mokrejs
2012-05-07 18:11 ` Daniel Pocock [this message]
2012-05-07 18:27 ` Martin Mokrejs
2012-05-07 23:30 ` Daniel Pocock
2012-05-08 8:21 ` Martin Mokrejs
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