Re: SSD mystery deepens



root <NoEMail@xxxxxxxx> wrote:
root <NoEMail@xxxxxxxx> wrote:
All speed tests mentioned here come from hdparm -t /dev/sda

In an earlier post I wondered about the decreasing performance
of my 240GB Corsair F3 SSD. Some useful suggestions were
given about changes to be made in /etc/fstab to ensure
best performance and longer life for the SSD. Among others,
these suggestions include noatime, discard, nodiratime.


I also read the Wikipedia article on SSD which mentioned
TRIM. I made the changes suggested and rebooted my system.
The Wiki article suggested that it is not good to have
your SSD run near capacity. I had partitioned the drive
into two partitions of 120GB each. So, I used gdisk
(previously I used fdisk) to wipe the partition information
and create a new 240GB partition (really 227GB).
I re-installed my OS and found a 35% speed degradation.

Here is a summary of my experience.

1. Immediately after buying the drive and installing it.
no OS, no FS speed= 475MB/s
2. After partitioning into 2 120GB partitions and installing
an ext4 system with my OS speed=318 MB/s
3. After re-partitioning with 1 240GB partition, ext4 FS,
and my OS speed=228MB/s

At this point I decided to return the drive, each install
of the OS caused about a 33% reduction in the speed

In preparation for returning the drive I nulled out
the drive with:
dd if=/dev/zero of=/dev/sdb (I had switched the drive to sdb).

4. After zeroing out the entire drive I ran another speed test
and found speed=386MB/s
5. Encouraged I put an ext4 FS but no OS: speed=479MB/s

6. Wow, I was back in business, so this time I re-installed
the OS and was back to speed=228MB/s

I am completely baffled by these results. Anyone with the
slightest idea of what is happening?

I have sent email to Corsair but I don't expect anything
from that.

The results are somewhat repeatable, except that I am
unable to regain the 318MB/s speed that first obtained.

The 228MB/s speed holds whether I use fdisk or gdisk
to partition the drive, and whether the drive is
partitioned as a single 240GB partition or 2 120GB
partitions.


I think I understand what the problem is: the hdparm test
doesn't mean anything. I just ran a real test that involved
lots of real disk i/o. The results with my sata3 spinning
disk took 15m 16s. The same test, with the same data
on the ssd took 4m 4s. So the ssd is at least 3.75
as fast. I say at least because there was considerable
output to the screen during the test.

I think this will finish me efforts with the ssd. I want
to thank everyone for contributing to the thread.
.



Relevant Pages

  • Re: Status of SSDs under Fedora ?
    ... SSD using gparted. ... I have not done any disk optimizations whatsoever. ... Also below is a crude perl script called by udev to "hotplug" mount ... If the partition is ext4 and the disk supports TRIM the "discard" mount option is also set ...
    (Fedora)
  • Re: [opensuse] Re: Temp directories NOT cleared at boot (oS13.1)
    ... you're using an SSD, since there are no moving parts in an SSD? ... One machine I used had 5-channel memory, difficult to do properly unless you use very small memory chips. ... If you have a SSD you can still partition it. ... perhaps a reliable 4T drive is more failure-resistant than four 1T drives. ...
    (SuSE)
  • Re: WD Black2 Probleme
    ... Programm vorhanden ist, dann gibt es nicht zuerst ein Plattmachen und dann eine Neuinstallation. ... Und wenn man die SSD platt macht, dann ist dieses Programm nicht mehr auf dem partitionierten Teil der SSD vorhanden und es gibt Probleme in der Erkennung der nachfolgenden Festplatte. ... Also einfach mal zuerst partitionieren oder eben viel einfacher: Einen Restore von Partition C: durchführen. ...
    (de.comp.hardware.laufwerke.festplatten)
  • Re: SSD (again)
    ... Updated the SSD to firmware v6 yesterday. ... restore, at which point I'll also do the alignment. ... Cleared the SSD and created an aligned partition as per the instructions ... but Drive Snapshot refused to restore to it as the partition size ...
    (uk.comp.homebuilt)