[SSD] partition alignment during 11.2 install

I’m installing 11.2 on a new system with an ssd. To increase performance I want to align the partitions.

Can this be done during the installation process?

During partition setup I did find the option for setting the block size (auto, 1MB, 2MB etc.). If I set the block size to 1 MB does this automatically align the partition as well? Or should I log in with a second shell to align the partitions during the installation process?

Aligning filesystems to an SSD’s erase block size | Thoughts by Ted

I just partitioned mine. It’s fast as lightning. These matters are too much on the tech side.

I just know Ted is the SSD man. Boot from a live-cd, follow Ted’s instructions, then install 11.2, at partitioning pick Rescan Devices. It will read the partition table from the SSD. Install and you should be OK.

Thanks for the link! What do you mean “too much on the tech side”? Should this topic be moved to another subforum?

Ted uses:
fdisk -H 224 -S 56

But in the first post of another forum they recommended:
fdisk -H 32 -S 32

Is this dependent on the size of the partition? Also, I want to make 4 partitions: boot, root, home and swap (I’m aware that people discourage the use of home and swap on an ssd, but that’s another discussion :wink: ). Should I align all four partitions or just the first one (boot)? If not, does this mean I only have to make the first partition using the live-cd and create the other ones during the installation process?

IMO SSD’s should only be used for relatively static data. Files that are rewritten or changed frequently should be on a hard drive. This is due to the nature of the SSD erase function which you should really read up on. You know that you can only erase an erase block about 10K times. Yes there are spares. But on very busy files 10K is nothing.

Alignment is a good idea but remember that the total number of files you write is dependent on the block size. So if you set block size to 1meg a 1 byte file will consume 1block or 1 meg of the drive.

Entropy always wins.

IIRC the Intel X25-M SSD (which I have) has 100K writes. The opinions on writing a lot on SSD’s are pretty divided, but I intend to use the SSD to the fullest. It has trim support (not yet supported by 2.6.31, I know, this summer I will upgrade to OS 11.3) and I will set kernel swappiness to zero.

According to this blog post:

No SWAP Partition, Journaling Filesystems, … on a SSD? | Robert Penz Blog

it should be fine. Either way I don’t intend to use the SSD for longer than 5/6 years and all my important data and downloads will be directly put/rscynced onto a RAID 1 array.

I used the fdisk options in Ted’s blog post (thanks Knurpht!), but now I encountered another issue:

During booting the kernel (I think it’s the kernel), says: “Waiting for /dev/sda3 to appear”. This is caused because during install I plugged out the raid array. Now the raid array is back in and the ssd is not sda anymore, but sdc. I’m then prompted to “fall back on /dev/disk/by-id…” which is the correct one and then it works fine.

Where can I fix this so the kernel (or is it still GRUB?) looks directly there?

I don’t know for sure, but let me guess. Try looking in /etc/fstab
You should be able to add/remove/edit entries. You do not have to mount drives using sdN notation. You can use UUID or even labels. As you see, when bios order changes, the sdN notation changes and that’s a real problem. Therefore, I use another method to identify drives. (I like labels.)

Has anyone figured out why Ted suggested 224 and 56? I read his blog post several times but I still do not understand it :stuck_out_tongue:

The key thing is that you want to match the erase block size of your SSD. The OCZ forum where they recommend -S 32 -H 32 is pretty ideal for the OCZ Vertex drives. Ted was going for a different block size.