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Does copying an image to an SSD cause partition misalignment?

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May 1, 2010 4:04:27 AM

Anybody know if copying a Norton Ghost 15.0 image to a pair of new Crucial C300 128GB SSDs in RAID 0 will cause the partition on the array to become misaligned? Any tips on using Ghost with Windows 7 x64 would be greatly appreciated.
a c 127 G Storage
May 1, 2010 10:48:51 AM

Likely you will find yourself with a misalignment yes.

And since you run RAID0 this misalignment would be DOUBLE the penalty.

So my recommendation is to install fresh, windows 7 to the RAID array. create a 200GB partition and leave the 56GB portion unused - since you won't have TRIM.

If you do not leave space unused, the performance and lifespan of the SSDs would degrade rapidly.
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May 1, 2010 2:20:54 PM

I'm not sure if it makes any difference, but I will be using a HighPoint RocketRAID 640 PCI-E 2.0 x4 SATA 6.0Gb/s Controller Card to connect my SSDs. From what I've read about this product, it comes with some pretty good tools and utilities. I hope it will have a tool or utility to compensate for the loss of TRIM.

Thanks for the recomendations. I will do that once my RAID hardware controller arrives - should be here within a few days.
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a c 127 G Storage
May 1, 2010 2:33:36 PM

By leaving space unused you can cope with not having TRIM. If you do not do this, performance and lifespan of your SSDs would continue to drop. At least reserve 15% as bare minimum; preferably 20-25%.
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May 1, 2010 3:08:38 PM

http://www.tomshardware.com/forum/258146-32-intel-raid-...

Would I be better off using the onboard RAID controller of the X58 motherboard instead of the hardware RAID? I read in the other thread titled "Intel SSD's in RAID 0 and using TRIM" that this would allow me to use TRIM. Or maybe this is only the case with the Intel SSDs not the Crucial C300.
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a c 127 G Storage
May 1, 2010 3:13:25 PM

No Windows RAID currently allows you to have SSDs in RAID with TRIM enabled.

The newer Intel drivers do allow TRIM to be used on an SSD connected to the onboard controller which is set to RAID mode because of a RAID-array with HDDs. Previously that meant you also didn't get TRIM even though your SSD was not part of the RAID. Now that Intel drivers passthrough the TRIM command in AHCI mode; this works just like the Microsoft AHCI driver supports TRIM.

But it does not allow to run SSDs in RAID while having TRIM enabled. Only Linux/BSD can use TRIM in RAID-mode for the moment. There will be a driver update one day that fixes this.

For the moment, if you want RAID0 you would need to sacrifice space. And even with TRIM doing this will increase your performance over time, especially if your SSD is at least 60% full.
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May 1, 2010 3:37:12 PM

Thanks for the info. I'll stick with my original plan and use the RocketRaid 640.

Here's a question that's more on the topic of the thread: What if I resize the C drive partition to 200GB with Disk Manager (it's currently 268GB but has 186GB free space), image the partition with Ghost, and then copy it to a newly created (aligned) 200GB partition on the RAID array? Would that preserve the alignment? The reason why I would rather use Ghost is because I've installed a lot of programs since my Windows installation, and I would rather not have to re-install.
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May 1, 2010 9:43:50 PM

Forgive me for being such a noob at this stuff, but how does the System partition affect the alignment? Norton Ghost 15.0 shows me a system partition that's 100MB in size. Does this partition need to be imaged separately or will it be included in the image of drive C? If separately, will this partition need to be aligned as well?
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May 2, 2010 3:10:40 AM

sub mesa said:
By leaving space unused you can cope with not having TRIM. If you do not do this, performance and lifespan of your SSDs would continue to drop. At least reserve 15% as bare minimum; preferably 20-25%.

What do you mean by "unused space"? unpartitioned or just free space in partitions?
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a c 127 G Storage
May 2, 2010 5:17:08 PM

unpartitioned space that has never been written to before, at least not since the last Secure Erase.

If you make your C: span the entire drive, and only have 10% full - then initially 90% will be free for the SSD. But over time, any writes and deletes will make the SSD think the entire drive is in use (all LBA sectors written to at least once) even though you have 90% free space on C: you still ran out of free cells on the SSD.

That's why you need to use partitions to prevent windows from writing to that 'reserved' space at all.

That is also why this trick does not work on a used drive - you have to do a Secure Erase first then reserve the space by not partitioning the whole disk. Only then does this work like intended.
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May 10, 2010 2:56:26 AM

sub mesa said:
unpartitioned space that has never been written to before, at least not since the last Secure Erase.

If you make your C: span the entire drive, and only have 10% full - then initially 90% will be free for the SSD. But over time, any writes and deletes will make the SSD think the entire drive is in use (all LBA sectors written to at least once) even though you have 90% free space on C: you still ran out of free cells on the SSD.

That's why you need to use partitions to prevent windows from writing to that 'reserved' space at all.

That is also why this trick does not work on a used drive - you have to do a Secure Erase first then reserve the space by not partitioning the whole disk. Only then does this work like intended.


I've decided to scap my SSD in RAID 0 idea all together - it just doesn't seem worth the hassle. So, unpartitioned space is not needed for non-RAID SSD drives.... correct? Does TRIM work with all brands of SSDs or only the Intel brand?
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a c 127 G Storage
May 10, 2010 3:22:23 PM

All controllers that support TRIM; modern Indilinx, Intel, Sandforce, Micron. Most/all JMicron do not support TRIM; Samsung i'm not sure but its a crap controller like JMicron. Toshiba is a JMicron controller really, but due to their bad reputation they changed the name on the chip to Toshiba instead to make it sell-able.

By not using RAID but instead using AHCI mode for single SSDs connected to your motherboard SATA ports, you would have TRIM capability with the right OS. So you need:
  • TRIM-capable OS (Windows 7, modern Linux, modern FreeBSD)
  • TRIM-capable filesystem (NTFS, Ext4, UFS)
  • TRIM-capable drivers (only in the case of Windows; early intel drivers did not support TRIM; if you have non-intel chipset do not use the chipset drivers from ATi/AMD/nVidia/ALi/ULi)
  • TRIM-capable SSD (Intel, Micron, Sandforce, Indilinx)

    By having TRIM, any free space on your NTFS filesystem can be used by the SSD internally. That means you're OK - at least if you keep a healthy 30% free.

    There are some reasons to still reserve space even with TRIM capability though. Due to there being no 'dedicated' large portion being available to the SSD, the internal and 'external' (visible) data will be scattered across the surface and cause what is known as "erase block fragmentation"; internal fragmentation. This is still an issue Intel is investigating; it may be addressed in a later firmware release.

    By reserving a dedicated portion of 20-50% to the SSD, you make sure it stays fast even after a long time. Rumors exist that next X25-E "enterprise" SSD will have 50% capable invisible and used internally only. These drives do not need TRIM at all. The X25-M that are out now have 8% space reserved already:



    The Anandtech article also displays a IBM-research graph plotting the spare factor against write amplification:



    Spare factor 0.1 would be close to the standard 8% reserved space on Intel SSDs. If you reserve more space, you'll see write amplification go down.

    So it is a balance between storage capacity and performance. The more storage space you sacrifice, the higher the performance over time; though i'd say the gain becomes very low after 50% reserved.
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