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I recently bought a W500 with a 256gb samsung ssd drive. Now it seems ridiculously slow at writing. I am copying files at about 30mb/s, but I can read them at about 200mb/s.

I tested it with the AS SSD Benchmark v1.4, and got a sequential writing speed of 34.64mb/s and reading speed of 196.95mb/s

When I bought it the drive had only been in use for about 240 hours, and according to the CrystalDiskInfo app it had 98% health.

Is there a bottleneck here somewhere? Or is the drive just plain bad. I'd really love it if someone could help me find some answers.

The main relevant (I hope) w500 specs for this machine are;

  • T9600 @ 2.8GHz
  • 4GB DDR3

Benchmarking screenshot.

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The write speeds and write latency are definitely slow. This answer mentions that AHCI-mode must be enabled in the BIOS:…. This is probably mainly so that the SSD's controller can take advantage of native command queuing ( – sblair Mar 19 '10 at 11:49
I tried switching from compability mode to AHCI, but I get a bluescreen while booting windows. – cc0 Mar 19 '10 at 16:22
It seems I have no AHCI driver installed, when I try to install this (…) driver it gives me a popup error saying my system does not meet the minimum requirements. I am using win7 64-bit, which should be correct for this driver. Any idea here? – cc0 Mar 19 '10 at 16:39
Ok, I fixed the problem of the AHCI with this post here; However it did not help performance anything at all. Any other suggestions? – cc0 Mar 19 '10 at 17:15
Hi look at this review and the write benchmarks are not slow for the pm800 in a dell xps 1645. I have the 256 GB and I'm seeing very low writes...arround 19mb. I'm going to try changing the driver... – fhuete Jun 14 '10 at 1:25

You use windows XP which assumed drives have 512 bytes sectors and which transfers files in chunks of 512 bytes.

However this is no longer the case with modern drives. Many modern harddrives use internal sector sizes of 4KB. If you only write 512 bytes to a 4096 bytes (4KB) sector the drive will need to read all 4K, change the 512 bytes, and rewrite it.

That is a lot of overhead. (as you can see below)


With SSDs it is even worse.

SSDs can not write to an already used sector. They only have three options:

  1. Find an empty, completely unused part and write a large (mostly empty) block to that.
  2. Read some data and write a fuller block, marking old data as unused.
  3. Wipe a part of the SSD. Usually in chunks of at least 1MB. (Hello overhead)

Graphically explained:

State before:  [empty][empty][empty][empty]    [empty][empty][empty][empty]  
Single write:  [data] [empty][empty][empty]    [empty][empty][empty][empty]   
               \                          /    \                          /
                 -------------------------      --------------------------
                  Flash 'sector' on disk                 Next cell

Speed would still be high, but you will eventually run out of empty sectors. When that happens:

First sector gets changed:

State before:  [used][used][used][used][used]    [empty][empty][empty][empty]  
State after:   [old] [old] [old ][old ][old]     [DATA] [used] [used] [used]
               \                          /      \                          /
                 -------------------------        --------------------------
                  Flash 'sector' on disk                   Next cell

Because the drive could not write to the first sector it read all of the data.
It then marked the old sectors as no longer being relevant (but not empty) and wrote to a new clean cell.

The old cell is left with unused data. It can be erased (back to [empty]), but that typically can only be done with groups of 1MB or 2MB worth of cells and takes a long time.

That means that:

  • Either the drive does this when it is idle (true for some drives)
  • Or after a while writes get real slow.

A modern OS is aware of the nature of SSDs and does a few things to help it (look up TRIM), Windows XP is not.

That was the first reason things would get slow with SSDs and XP.

There is a second item which also slows things down. NTFS (used as default by windows XP) has a 4KB sector size for its filesystem.

If that is aligned with the cells on the drive then things are not fine. If it is not then you get double the problems.

Unaligned example
4KB of data in a NTFS part:       [DATA] [DATA]     [DATA] [DATA]
Cells on the drive: [empty][empty][empty][empty]    [empty][empty][empty][empty]  

Notice the overlap of the NTFS write and two of the SSDs cells? Not good.

Smart partitioning can help with this, but you do that during installation of XP, and you must manually select good values.

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For what it's worth, I have the same cheap Samsung PM800 that Dell ships and the benchmarks are close to that. Looking around on the Internet, it seems these drives are just slow.

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Please don´t settle with that "cheap SSD" answer...look at the link I posted above You will see writing speeds of around 170MB for PM800, almost 6 times faster than what cc0 reported. I've been doing a lot of research and tests with my computer. I was around 15 MB for seq write! But now, trying different drivers, I'm seeing 141.1 on Cristal DiskMark.

I'm not an expert but I'll suggest you review the firmware version for your SSD to check if TRIM is enabled. The number in the firmware must be over 18. Inf not there is a firmware available form samsung, just google it. Also I'm getting better results with old Intel’s matrix storage drivers rather that the new rapid storage. Finally even though many discard this rate, I think a good "proxy" is the windows experience index. An SSD MUST perform over 5.9, which is the "roof" number for a standard HD. I was stacked at 5.9 for the HD but now I’m in 6.5.

There is a weird performance issue that I've not been able to isolate...I'll keep trying nd get back later...

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"check if TRIM is enabled" And should it be enabled or disabled? What are the effects of changing this setting? – David Richerby Oct 1 '15 at 8:43

Installing the latest firmware from either through Dell or Samsung will enable TRIM support for this drive, I restored my image unto the SSD after flashing the firmware and my writing speeds are now back to when I purchased the drive.

I highly recommend anyone that is still experiencing these slow write issues to apply the latest TRIM enabled firmware for the PM800 from Samsung.

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Where may I find this driver? I seem unable to find the appropriate one. My firmware version is VBM15D1Q (Dell), is there any solution for this? – cc0 Nov 6 '10 at 13:28

If you have Windows XP. Windows XP was never designed for modern SSD drives. Especially if the drive is using 4K sector sizes (which all modern drives since around late 2010 are). Then you need to run a sector alignment tool. I know that Samsung has one on their download site as well.

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This is the answer;

The VBM15D1Q does not support TRIM, nor will it ever. Nor was it marketed by Dell / Samsung as TRIM-capable. So that's the end of the story. There are multiple threads out there and also an official post by Dell with a list of which versions of the pm800 drives support TRIM and which does not.

Sad face.

edit:tony trim helps a bit for a little while

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Update: still amazingly bummed about how slow this is. It took me a whole hour to install fallout 3 on it because the write speeds are so slow. Ridiculous. – cc0 Dec 29 '10 at 9:54

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