There are many posts about correct partition alignment and SSDs on the web. I would like to share with you my personal experiences. It is true that the standard Windows XP and Linux partitions, which start at sector 63 are definitely not optimised for SSD usage, particularly generation 1 SSDs (like the OCZ Core V2 I own). Putting all technical explanations aside I can only impart the frustrating stuttering that occured using a standard alignment whenever the disk was put under any kind of load the system would hang for seconds at a time. I read and digested Theodore Tso’s article about a 56 sector alignment and ran that setup for several months.
While the 56 sector setup was definitely better than the standard 63 I still couldn’t help thinking that I should get better performance out of the OCZ particularly after the large disparity between the SSDs in the Photofast review. So reading further I decided that whatever erase block size the OCZ had it would be best served by a partition which starts and aligns on the 1Mb boundary (sector 2048) since that is divisible by all the likely block sizes up to and including 1MB.
I used parted and made sure that the partitions ended and started on a sector divisible by 2048 and then copied the partitions back (this would generally mean leaving a gap of just under 1MB between each partition). There was a difference in performance and dd averaged around 89MB per second writing, which I don’t think is bad for a first generation SSD. So the moral of the story is to optimise for SSD by using a 1MB partition boundary.
On a not entirely unrelated note I also wanted to set up the partition table as GPT to get around the 4 primary partition limitation of MSDOS partition tables. I managed to create everything successfully and even created a “bios_grub” partition to install grub into but never managed to get it booting. If anyone know of any obvious steps I missed there please let me know. Interestingly I was able to create a new MSDOS partition table with Gparted, recreate the partitions with the same starting and ending sectors and the data was still there, so at least I didn’t have to copy it again (good job I was a bit bleary eyed at that stage).
Anyway here is my current partition layout for information:-
Model: ATA OCZ CORE_SSD (scsi)Disk /dev/sda: 125206528sSector size (logical/physical): 512B/512BPartition Table: msdosNumber Start End Size Type File system Flags1 2048s 309248s 307201s primary ext2 boot2 311296s 17577984s 17266689s primary ext33 17580032s 125204480s 107624449s primary ext3
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