Hi, I'm about to setup a new Arch box and wanted to use GPT instead of the (old) MBR partition scheme, just for the fun of it ;). I've read through the various articles in the wiki, but it seems that something strange is going on here. I'm about to install the system to a SSD (Kingston S100), therefore I also have to consider proper alignment. I've created the partition scheme with gdisk (alignment set to 2048 boundary, although I've tried it with different values (up to 8192), too), which basically looks like that: Number Start (sector) End (sector) Size Code Name 1 2048 264191 128.0 MiB 0700 Linux/Windows data 2 264192 31277198 14.8 GiB 0700 Linux/Windows data Take a look at the start sectors, they should be properly aligned to 2048, as 264192 is dividable by 2048. In order to check the proper alignment I've run hdparm -tT over both partitions, here are the results: /dev/sda1: Timing cached reads: 12026 MB in 2.00 seconds = 6017.15 MB/sec Timing buffered disk reads: 128 MB in 0.64 seconds = 201.56 MB/sec /dev/sda2: Timing cached reads: 12086 MB in 2.00 seconds = 6047.19 MB/sec Timing buffered disk reads: 278 MB in 3.02 seconds = 92.02 MB/sec Quite a huge discrepancy considering the fact that a SSD should have roughly the same speed everywhere. Well, after fiddling around with it a little bit, I've finally tried the same setup with the old MBR partition scheme, using fdisk, which gave me the following partition scheme: Device Boot Start End Blocks Id System /dev/sda1 2048 264191 131072 83 Linux /dev/sda2 264192 31277231 15506520 83 Linux So the partition scheme is the same, despite the fact that the second partition is a little bit bigger with MBR as there is no copy of the partition table. With the MBR partitions I get the following results using hdparm -tT in order to measure the speed: /dev/sda1: Timing cached reads: 11578 MB in 2.00 seconds = 5793.15 MB/sec Timing buffered disk reads: 128 MB in 0.63 seconds = 202.22 MB/sec /dev/sda2: Timing cached reads: 11896 MB in 2.00 seconds = 5952.79 MB/sec Timing buffered disk reads: 604 MB in 3.00 seconds = 201.16 MB/sec So, both partitions are, as to be expected, equal in speed. I'm quite astonished by these results, which confuse me totally. Is it possible that GPT is slower than MBR? Is there something wrong implemented within gdisk? Is there any explanation to that? Right now the only thing I can do to get full speed is to use MBR once again :(. Best regards, Karol Babioch
Attachment:
signature.asc
Description: OpenPGP digital signature
