Salient Soft

Update 7/10/2010

I had some further issues when trying to realign the boot partition of an OCZ Vertex 30GB SSD on an Intel D510 dual core atom ‘always on’ silent pc running Windows XP Pro.
I tried the technique used before below, using diskpar to create the partition and then using Acronis True Image 2010 to restore first the NTFS partition, then restoring the MBR and track 0 as a second subsequent operation. In order run diskpar standalone, I created a bootable CD containing diskpar using Bart PE, as I found that booting a Windows XP CD into recovery mode does not give you full command prompt capabilities – you cannot run an arbitrary .EXE utility at all (a real surprise to learn) – you can only use the commands listed. All this was done as below (see here) so as to force Acronis to re-use the partition created by diskpar. Unfortunately allthough the process went smoothly the resulting system would not boot, citing NTLDR/boot loader problems.

I then upgraded to Acronis True Image Home 2011 and also Acronis Disk Director 11, as these were both supposed to be SSD friendly and handle the alignment correctly. I deleted the partition and restored the original backup with the incorrect alignment, allowing Acronis to create the partition itself, and the system booted fine as before. I then used Disk Director to slightly shrink the partition to ensure that there was space to allow it to realign – there should have been a few MB on the end anyway, but I shrank it by 100MB to be really sure.

I then did a full standalone backup of the system disk with the shrunken partition. I found that just restoring that backup (shrunken but with the wrong alignment) with True Image 2011 was not enough – the incorrect alignment was still present on the SSD, i.e. it appeared that True Image always gives priority to the partition details in the backup. In hindsight it may have been possible to override the partition settings during the restore to cause Acronis to fix the alignment by using ‘new’ partition settings but I did not try – if so, this might have fixed the alignment problem in one go.

However, Disk Director 11 was able to delete and then recreate the partition correctly, i.e. when it created a new partition on the SSD it automatically used the correct alignment (1048576 bytes or 1MB), as confirmed afterwards by diskpar. I created a partition to fill the disk, as I knew that True Image would happily restore the slightly smaller shrunken one to a larger one. I then used the same technique as above with True Image Home 2011, i.e. restore the NTFS partition first without the MBR and track 0, then restore MBR and track 0 as a second operation after the restore.

This time, it all worked fine and I ended up with a bootable system with the correct partition alignment. I’m not sure what the issue was – perhaps the shrinking first fixed it. I do know that this technique has worked fine for me previously as below, when I backed up a 2.5" laptop hard drive via Acronis True Image, created an aligned partition on a new SSD with diskpar, and then restored the backup to the SSD with the same trick.

The resulting lessons learned seem to be as follows:-

1. Use Disk Director 11 with SSDs, alignment will be correct, and you can easily do it standalone by creating a Disk Director boot CD.
2. Using True Image 2011 is also recommended – it is stated to be SSD friendly and is better all around.
3. However, care is needed when restoring an SSD backup with the wrong alignment, as by default even True Image 2011 keeps the wrong alignment. Either the technique above is needed or it may be possible to get Acronis to use ‘new’ partition settings to override the ones in the backup, in which case the restore can all be done in a single step.
4. to be safe, when correcting wrong SSD alignment, shrink partition first by say a few 10s of MB to be sure (I used 100MB) to ensure there is no funny truncation when it is restored and realigned.

I have not done any performance comparisons before and after the realignment, but have confirmed that the alignment is now correct. Whilst I have seen posts on the internet that suggest lower alignment values than 1MB, both Windows 7 when it installs to an SSD, and Disk Director 11 use 1MB (1048576 bytes), so I am sticking with this value.

Original Post

Partition alignment is important for SSD performance to avoid unnecessary read/write cycles. Windows 7 appears to handle this but Windows XP does not. The partition alignment must be set manually when creating it (with diskpar or diskpart – diskpar seems to be preferred as it displays the partition offset in bytes so that the resulting offset can be accurately seen, even though diskpart is newer and has more features)

When restoring or cloning disks with Acronis True Image Home 2010, the original partition alignment is kept providing the operation does not recreate the partitions. See the Acronis forums here for details.

The OCZ forums have some articles on how to create correctly aligned partitions here and here.

Another step by step guide to cloning to an SSD with Acronis may be found here. When doing this, do not (as I did) forget the step which says to set the restore partition as primary and active in Acronis! In my case, Acronis made the wrong partition active so the SSD would not boot. It was simple enough to change – boot a system which can see the disk, then use disk management, right click the correct boot partition and select set as active. It is not necessary to repartition the SSD and re-restore the Acronis backup.

A good balanced article about optimising Windows XP for SSD use is here. There is a lot of misinformation around for example about the performance effects of swap files, which is based on misunderstandings about windows swap file usage, and also based on older SSDs with short service lives. The more informed wisdom appears to say that you should not disable the swap file as it will not make a significant difference.

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