Yes indeed. As soon as I sent you last email I realized that and set
the write back option. Now I get 130MB/s better but still nowhere
close to 600MB/s as advertised or what others say one should see.
What are your recommendations about HW choice? What is more
preferrable and better?
Another question do I need to set WCE on all the disks first before
creating RAID0? Or can I do that after creating RAID0? I tried to set
WCE on existing RAID0 but it fails "change_mode_page: failed fetching
page: Caching (SBC)".
sdparm --set=WCE --save /dev/sda
/dev/sda: FUJITSU MBD2300RC D809
dd if=/dev/zero of=/dev/sda bs=128k count=80k oflag=direct
81920+0 records in
81920+0 records out
10737418240 bytes (11 GB) copied, 82.8041 seconds, 130 MB/s
Thanks for your help as always.
On Wed, Apr 20, 2011 at 5:53 PM, Joe Landman
<landman at scalableinformatics.com> wrote:
> 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
>
