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Re: [OCLUG-Tech] any personal experience out there with hybrid SSD drives?

  • Subject: Re: [OCLUG-Tech] any personal experience out there with hybrid SSD drives?
  • From: R RENAUD <rjrenaud [ at ] rogers [ dot ] com>
  • Date: Fri, 6 May 2011 12:49:57 -0700 (PDT)
--- On Fri, 5/6/11, Paul B. <red [ dot ] line [ at ] rogers [ dot ] com> wrote:
> Roland,
> great results, but I'd like to request one clarification:
> did you constrain the hdd benchmark with the same ramdisk
> size as the 
> SSD, or did you mess around with the ramdisk size only
> after running the 
> comparison test?

Having checked my notes in more detail, I find the answer is neither,
I got the information from the internet before purchasing a drive.

However, as I mentioned in my previous post, it's noticably faster.
My systems with non-SSD disks sometimes have me wondering why they
seem slow until I remember I'm using a spinning disk.
The big gain is on seek time and latency.

I purchased the Crucial RealSSD C300 64GB mainly because of
the price (this was a test) and it had enough storage for me.
Data from my original WD Scorpio Black 320GB is available via a small
USB external HDD Enclosure (was $14 now $11 ).

I spent a while reading about SSDs.
1) Will they work with Linux?
2) What's the price range?
3) Although I'm mainly interested in building a quiet computer,
   how will the speed compare with my existing disk since some
   versions of the technology have very slow write speeds.

Here are my notes:
I've left out the price information to save space and since prices
have reduced significantly.

10/11/04
    - Excellent description of SSD write life expectancy and operations.
      http://www.anandtech.com/show/2829
	The SSD Relapse: Understanding and Choosing the Best SSD
	by Anand Lal Shimpi on 8/30/2009 12:00:00 AM 
	- Intel drives are the only ones that perform well.
	  - The controller is important.
	- Nand flash has to be written 4KB at a time.
	- Nand flash has to be erased 512KB at a time.
	- A flash memory cell starts to fail after 10,000 writes.
	  Therefore, s/w must know how to block the writes and not
 	  keep re-writing the same cell.
        - Author finds (in Aug 2009) best drives are:
	  Intel X25-M
	  OCZ Vertex (based on Indilinx controller)
	- Even the slow SSDs are fast with low power consumption.

    http://torvalds-family.blogspot.com/2009/03/ssd-followup.html
	Linus' blog - Wednesday, March 18, 2009

    http://ssd-reviews.com/
	SSD comparison database


10/11/05
  - finished reading very good article
      http://www.anandtech.com/show/2829
	The SSD Relapse: Understanding and Choosing the Best SSD

    Note: Newer data.  Crucial C300 256GB is fast.
    http://www.tweaktown.com/reviews/3118/crucial_realssd_c300_256gb_sata_6gbps_solid_state_disk/index11.html
        Crucial RealSSD C300 256GB SATA 6Gbps Solid State Disk - Feb 3, 2010
    shopRBC has:
    Crucial RealSSD C300 64GB 2.5" SATA 6GBs Solid State Drive - $147.00

    Intel X25V 40GB 2.5" SATA Solid State Disk	   	       - $139.00
        X25-V MLC Solid State Drive 

  - Linux tweaks.
      Read this if buying an SSD.
        http://tombuntu.com/index.php/2008/09/04/four-tweaks-for-using-linux-with-solid-state-drives/
	Four Tweaks for Using Linux with Solid State Drives - Sep 2008
	- Mount ext3 volumes with relatime instead of noatime.
	- Use ramdisk.
	    /etc/fstab
	      tmpfs /tmp tmpfs defaults,noatime,mode=1777 0 0
        - Put Firefox cache in ram.
	      Open about:config in Firefox. Right click in an open
	      area and create a new string value called
	      browser.cache.disk.parent_directory. Set the value to /tmp.
        - Change IO scheduler from
	    % cat /sys/block/sda/queue/scheduler   (rjrl5 CentOS 5.3)
	        noop anticipatory deadline [cfq] 
	  to
	    % echo deadline > /sys/block/sda/queue/scheduler

          There are more details.  Read the article.
	  Also read the user responses.
	  - MadMike says relatime is now standard with Ubuntu.
	  - Moving /var/log to tmpfs is also interesting.
	  - June 25, 2010 entry says:
	      Solid State disks now run straight out of the box for Linux.

        http://www.linux-mag.com/id/7345
	    NILFS: A File System to Make SSDs Scream - Jun 2009
	    NILFS2 (New Implementation of a Log-Structured File System
	    Version 2) is a very promising new log-structured file
	    system that has continuous snapshots and versioning of the
	    entire file system.
	    ... good performance on SSD drives.


10/11/23
  - speed comparison between SSD and disk drives.

    http://www.bit-tech.net/hardware/storage/2010/07/21/crucial-realssd-c300-64gb-ssd-review/4
	
    Crucial RealSSD C300 64GB 2.5" SATA 6GBs Solid State Drive
    ATTO Disk Benchmark 
	1,024KB Compressable Sequential Read Speed 	360 MB/s

	1,024KB Compressable Sequential Write Speed	 80 MB/s

    http://www.bit-tech.net/hardware/storage/2009/10/02/western-digital-2tb-caviar-black-review/3
    Western Digital 2TB Caviar Black

    HD Tach
     Average Read					117 MB/s
     Average Write					 72 MB/s

    
    Western Digital 2TB Caviar Green
     Average Read					 79 MB/s
     Average Write					 53 MB/s

    http://www.legitreviews.com/article/955/2/
    WD Scorpio Black 320GB 7200RPM 16MB 2.5" SATA Hard Drive
     Average Read					 71 MB/s
     Average Write					 66 MB/s

  10/12/04
  - summary: Crucial RealSSD is 5 times faster on read and 20% faster
    	     on write than WD Scorpio Black 320GB.

10/12/05
  http://www.zdnet.com/blog/perlow/geek-sheet-a-tweakers-guide-to-solid-state-drives-ssds-and-linux/9190
    Geek Sheet: A Tweaker's Guide to Solid State Drives (SSDs) and Linux
	 - Jason Perlow  Nov 18, 2010

    Use the "noop" simple I/O scheduler.
    - add block/sda/queue/scheduler = noop to your /etc/sysfs.conf
    (requires the sysutils package) or elevator=noop to the kernel
    boot parameters in your /etc/default/grub file

    Change the file system mount options on SSDs to "noatime" and
    mount your /tmp in RAM.
    UUID=aaf49668-2624-4238-a486-baf341361be6 /               ext4
              noatime,discard,data=ordered,errors=remount-ro 0       1 


Roland writes: (on May 5, 2011)
| I used "hdparm -t /dev/sda" on both drives for the read speed test.
| Offhand, I don't recall what I used to test writes.

I was in a hurry when I posted this.
Looking at my notes I find

  - speed tests described in article above
	Four Tweaks for Using Linux with Solid State Drives - Sep 2008
    Rrjrl5 % hdparm -t /dev/sda
    /dev/sda:
     Timing buffered disk reads:  332 MB in  3.00 seconds = 110.56 MB/sec

    Rrjrlap3% hdparm -t /dev/sda
    /dev/sda:
     Timing buffered disk reads:  666 MB in  3.00 seconds = 221.90 MB/sec

    Machines
      Rrjrl5   - Dell Optiplex GX620 Intel Pentium D 3.0 GHz  (dual core)
      	       - disk is Western Digital Caviar Black 500G
      Rrjrlap3 - ThinkPad T500 Intel Core2 Duo processor P8400 2.26GHz
      	       - disk is Crucial RealSSD

    http://www.thegeekstuff.com/2008/11/overview-of-ramfs-and-tmpfs-on-linux/
	Overview of RAMFS and TMPFS on Linux - Ramesh Natarajan Nov 6, 2008
    The notes in the "Tweaks" article below don't show how to set the
	ramdisk size.

Running the test on Rrjrlap3 again a few times, I get:
Rrjrlap3% hdparm -t /dev/sda

  /dev/sda:
   Timing buffered disk reads:  634 MB in  3.01 seconds = 210.77 MB/sec
   Timing buffered disk reads:  656 MB in  3.00 seconds = 218.59 MB/sec
   Timing buffered disk reads:  634 MB in  3.00 seconds = 211.04 MB/sec
   Timing buffered disk reads:  634 MB in  3.00 seconds = 211.22 MB/sec

Conclusions:
- Running "hdparm -t /dev/sda" isn't a sufficient test to justify the
  purchase of an SSD.
  BTW: The one Robert Day is considering is a "hybrid SSD".
       I don't know anything about that or how it differs.

- Reading internet articles can give some interesting background but
  the speed tests are usually done on Microsoft operating systems.

- I think the main improvement with SSDs are reduced latency, less
  noise and less power consumption.

Note that since Linux usually writes data as a background job, write
speeds often aren't noticed.

Hopefully, the pointers above will be of interest to someone
considering an SSD.

roland