linux-kernel - Re: Performance Characteristics of All Linux RAIDs (mdadm/bonnie++)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.1.10.0805281329450.29755@p34.internal.lan>
Date:	Wed, 28 May 2008 13:32:44 -0400 (EDT)
From:	Justin Piszcz <jpiszcz@...idpixels.com>
To:	Chris Snook <csnook@...hat.com>
cc:	linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
	xfs@....sgi.com
Subject: Re: Performance Characteristics of All Linux RAIDs
 (mdadm/bonnie++)



On Wed, 28 May 2008, Chris Snook wrote:

> Justin Piszcz wrote:
>> Hardware:
>> 
>> 1. Utilized (6) 400 gigabyte sata hard drives.
>> 2. Everything is on PCI-e (965 chipset & a 2port sata card)
>> 
>> Used the following 'optimizations' for all tests.
>> 
>> # Set read-ahead.
>> echo "Setting read-ahead to 64 MiB for /dev/md3"
>> blockdev --setra 65536 /dev/md3
>> 
>> # Set stripe-cache_size for RAID5.
>> echo "Setting stripe_cache_size to 16 MiB for /dev/md3"
>> echo 16384 > /sys/block/md3/md/stripe_cache_size
>> 
>> # Disable NCQ on all disks.
>> echo "Disabling NCQ on all disks..."
>> for i in $DISKS
>> do
>>   echo "Disabling NCQ on $i"
>>   echo 1 > /sys/block/"$i"/device/queue_depth
>> done
>
> Given that one of the greatest benefits of NCQ/TCQ is with parity RAID, I'd 
> be fascinated to see how enabling NCQ changes your results.  Of course, you'd 
> want to use a single SATA controller with a known good NCQ implementation, 
> and hard drives known to not do stupid things like disable readahead when NCQ 
> is enabled.
Only/usually on multi-threaded jobs/tasks, yes?

Also, I turn off NCQ on all of my hosts that has it enabled by default because
there are many bugs that occur when NCQ is on, they are working on it in the
libata layer but IMO it is not safe at all for running SATA disks w/NCQ as
with it on I have seen drives drop out of the array (with it off, no problems).

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/