Re: Intel X25-M MLC SSD benchmarks - How can I be sure i am erased block aligned ?

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http://www.tomshardware.com/reviews/Intel-x25-m-SSD,2012-8.html
they say that write IO fluctuates.



On 12/12/08, Matthew Wilcox <matthew@xxxxxx> wrote:
> On Thu, Dec 11, 2008 at 10:40:41PM +0200, Raz wrote:
>  > > ________________________________
>  > > From: Matthew Wilcox [mailto:matthew@xxxxxx]
>  > > Sent: Thu 12/11/2008 5:44 AM
>  > > To: Raz Ben-Yehuda
>  > > Cc: linux-ide@xxxxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx
>  > > Subject: Re: Intel X25-M MLC SSD benchmarks
>  > >
>  > > On Thu, Dec 11, 2008 at 12:12:37AM +0200, Raz Ben-Yehuda wrote:
>  > >> I did not want to dive into details because it does not matter. Whether
>  > >> noop,deadline, deadline parameters...
>  > >> As for the controller I used 4 different controllers. Adaptec,AHCI and
>  > >> Intel as Integrated chips on the 1025W-UR supermicro motherboard, and a
>  > >> 4-th controller SuperMicro UIO Adaptec aac card.
>  > >> All gave same results for most dd writes commands.
>  > >> dd if=/dev/zero of=/dev/sda bs=1M count=1000 oflag=direct , and many
>  > >> other variants such erase block size ( 128K ) , several erase block size
>  > >> and so on. Kernel is 2.6.18-8.el5.
>  > >
>  > >>>OK, I suspect you aren't giving the drive enough work to do for it to
>  > >>>perform at its best.  Try doing something like this:
>  > >
>  > >>>for i in $(seq 0 9); do \
>  > >  >>     dd if=/dev/zero of=/dev/sda bs=1M count=1000 oflag=direct \
>  > >  >>               seek=$(($i * 1000)) & \
>  > >>>done
>  > >
>  > did that. nothing. also, I would like to note that IO flow is quite
>  > weird.iostats reports 70GB/s in the first few seconds, and then it
>  > degrades to 20
>  >  MB/s and less. could it be that I am not erase-block aligment ?
>
>
> That doesn't sound likely to me.  Erase block size isn't a huge issue
>  with these drives.  I've been trying to replicate your problem, but I'm
>  not having any luck; unfortunately I only have access to an X25-E drive
>  (not an X25-M) and I'm seeing 175-185MB/s when it's attached to an AHCI
>  controller, just with a single dd (I haven't even played with the
>  elevator).  I'm trying to get hold of an X25-M drive, but I don't know
>  when I'll receive one.
>
>
>  > how does SSD aligments interacts with a controller ?
>
>
> Controllers can generally send down large enough IOs that it isn't a
>  problem.  And the Intel SSDs are smart enough that you shouldn't have to
>  align to erase block boundaries to make them go fast.
>
>
>  --
>
> Matthew Wilcox                          Intel Open Source Technology Centre
>  "Bill, look, we understand that you're interested in selling us this
>  operating system, but compare it to ours.  We can't possibly take such
>  a retrograde step."
>
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