[Gluster-users] Performance

[Joe Landman]

On 04/20/2011 07:50 PM, Mohit Anchlia wrote:
> I did that but it looks the same. I did get an error even though it
> says write-caching is on.
>
> [root at dslg1 ~]# hdparm -W1 /dev/sda
>
> /dev/sda:
>   setting drive write-caching to 1 (on)
>   HDIO_DRIVE_CMD(setcache) failed: Invalid argument
> [root at dslg1 ~]# hdparm /dev/sda

You might need sdparm

	sdparm -a /dev/sda | grep WCE

With WCE on I see

	[root at smash ~]# sdparm -a /dev/sda | grep WCE
	  WCE         1

and with it off, I see

	[root at smash ~]# hdparm -W0 /dev/sda

	/dev/sda:
	 setting drive write-caching to 0 (off)
	 write-caching =  0 (off)

	[root at smash ~]# sdparm -a /dev/sda | grep WCE
	  WCE         0

You might need to change WCE using

	sdparm --set=WCE -a /dev/sda

or similar ...

>
> /dev/sda:
>   readonly     =  0 (off)
>   readahead    = 256 (on)
>   geometry     = 36472/255/63, sectors = 585937500, start = 0
> [root at dslg1 ~]# [A
> [root at dslg1 ~]# dd if=/dev/zero of=/dev/sda bs=128k count=1k oflag=direct
> 1024+0 records in
> 1024+0 records out
> 134217728 bytes (134 MB) copied, 8.10005 seconds, 16.6 MB/s
>
>
> On Wed, Apr 20, 2011 at 5:45 PM, Joe Landman
> <landman at scalableinformatics.com>  wrote:
>> On 04/20/2011 07:28 PM, Mohit Anchlia wrote:
>>>
>>> dd of=/dev/null if=/dev/sda bs=128k count=80k iflag=direct
>>> 81920+0 records in
>>> 81920+0 records out
>>> 10737418240 bytes (11 GB) copied, 83.8293 seconds, 128 MB/s
>>
>> Ok, this is closer to what I was expecting (really ~150 MB/s would make more
>> sense to me, but I can live with 128 MB/s).
>>
>> The write speed is definitely problematic.  I am wondering if write cache is
>> off, and other features are turned off in strange ways.
>>
>> This is a 2 year old SATA disk
>>
>> [root at smash ~]# dd if=/dev/zero of=/dev/sda2 bs=128k oflag=direct
>> dd: writing `/dev/sda2': No space left on device
>> 16379+0 records in
>> 16378+0 records out
>> 2146798080 bytes (2.1 GB) copied, 20.8322 s, 103 MB/s
>>
>> Write cache is enabled.  Turning write cache off (might not be so relevant
>> for a RAID0),
>>
>> [root at smash ~]# hdparm -W /dev/sda
>>
>> /dev/sda:
>>   write-caching =  1 (on)
>> [root at smash ~]# hdparm -W0 /dev/sda
>>
>> /dev/sda:
>>   setting drive write-caching to 0 (off)
>>   write-caching =  0 (off)
>>
>> [root at smash ~]# dd if=/dev/zero of=/dev/sda2 bs=128k oflag=direct
>> dd: writing `/dev/sda2': No space left on device
>> 16379+0 records in
>> 16378+0 records out
>> 2146798080 bytes (2.1 GB) copied, 155.636 s, 13.8 MB/s
>>
>> See if you can do an
>>
>>         hdparm -W1 /dev/sda
>>
>> and see if it has any impact on the write speed.  If you are using a RAID0,
>> safety isn't so much on your mind anyway, so you can see if you can adjust
>> your cache settings.  If this doesn't work, you might need to get to the
>> console and tell it to allow caching.
>>
>>
>> --
>> Joseph Landman, Ph.D
>> Founder and CEO
>> Scalable Informatics, Inc.
>> email: landman at scalableinformatics.com
>> web  : http://scalableinformatics.com
>>        http://scalableinformatics.com/sicluster
>> phone: +1 734 786 8423 x121
>> fax  : +1 866 888 3112
>> cell : +1 734 612 4615
>>


-- 
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics, Inc.
email: landman at scalableinformatics.com
web  : http://scalableinformatics.com
        http://scalableinformatics.com/sicluster
phone: +1 734 786 8423 x121
fax  : +1 866 888 3112
cell : +1 734 612 4615