Arch Linux

Stunts

Member

From: Portugal

Registered: 2009-03-28

Posts: 339

Website

Re: [SOLVED] Poor SSD Performance, Low Buffered Disk Reads

Oh sweetness!
Aligning the partitions to sector 6144 as recommended was further increased my disk speed to a blazing fast 510.86 MB/sec !
A big thanks to everyone in this thread who provided their experiences and insight.

TiZ

Member

Registered: 2009-02-27

Posts: 58

Re: [SOLVED] Poor SSD Performance, Low Buffered Disk Reads

I have the same SSD as OP, and have slightly lower speeds than him reported through hdparm. Which strikes me as funny because my laptop boots up and starts XFCE offensively fast. So I'd like to start getting those proper read speeds and make things even more ludicrous. Not to mention that I hear improper alignment can worsen disk wear. I've been using this SSD since December, so I'd like to fix this up sooner rather than later.

I keep hearing that realignment to sector 12288 has been successfully making things better, but how precisely do I do that? Is there a tool that will resize the file systems and partitions for me? I know gparted will do it, but it seems I can't tell it to align to a specific sector size. And it seems like gdisk only suports deleting and recreating partitions, not resizing them. Can command line parted do this somehow?

Stunts

Member

From: Portugal

Registered: 2009-03-28

Posts: 339

Website

Re: [SOLVED] Poor SSD Performance, Low Buffered Disk Reads

@TiZ:
I had to backup the partitions on my SSD, delete the existing ones, and restore the data from backup. It was fast and easy, and a good learning experience.
In the end I had to reinstall the bootloader using a chroot fom a live USB too. I also had, of course, to change the UUID of the partitions in /etc/fstab.
The wiki is your friend for a full system backup (it is what I used):
https://wiki.archlinux.org/index.php/Fu … with_rsync

WonderWoofy

Member

From: Los Gatos, CA

Registered: 2012-05-19

Posts: 8,414

Re: [SOLVED] Poor SSD Performance, Low Buffered Disk Reads

I also had, of course, to change the UUID of the partitions in /etc/fstab.

This is why I use filesystem labels.  I can rsync to an external disk, do 'sed -i 's/oldlabel/bkuplabel/g', boot that external shit!  Then repartition, re-mkfs, etc. etc.

Stunts

Member

From: Portugal

Registered: 2009-03-28

Posts: 339

Website

Re: [SOLVED] Poor SSD Performance, Low Buffered Disk Reads

I also had, of course, to change the UUID of the partitions in /etc/fstab.

This is why I use filesystem labels.  I can rsync to an external disk, do 'sed -i 's/oldlabel/bkuplabel/g', boot that external shit!  Then repartition, re-mkfs, etc. etc.

This.
That is a great idea. A lot less trouble and error prone than manually copying UUIDs... You live and you learn. =-)

schizo-ri

Member

From: Rijeka, Croatia

Registered: 2014-06-01

Posts: 25

Re: [SOLVED] Poor SSD Performance, Low Buffered Disk Reads

I still don't get it. I have OCZ Agility3.

# fdisk -l /dev/sda

Disk /dev/sda: 111,8 GiB, 120034123776 bytes, 234441648 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x3058731b

Device    Boot     Start       End    Blocks  Id System
/dev/sda1 *         4096  25169919  12582912  83 Linux
/dev/sda2       25169920 230690815 102760448  83 Linux
/dev/sda3      230690816 234441647   1875416  82 Linux swap / Solaris

# hdparm -Tt /dev/sda

Timing cached reads:   8938 MB in  2.00 seconds = 4470.88 MB/sec
Timing buffered disk reads: 826 MB in  3.00 seconds = 275.11 MB/sec

I think number should be higher and they were when disk was empty (~ 470 MB/sec for buffered disk reads) and even lower when system ran for several days (~ 120 MB/sec). EBS on all OCZ SSDs is 512Kb. To which sector should I align partitions to be aligned with EBS?

supermariolinux

Member

Registered: 2014-01-21

Posts: 11

Re: [SOLVED] Poor SSD Performance, Low Buffered Disk Reads

I still don't get it. I have OCZ Agility3.

# fdisk -l /dev/sda

Disk /dev/sda: 111,8 GiB, 120034123776 bytes, 234441648 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x3058731b

Device    Boot     Start       End    Blocks  Id System
/dev/sda1 *         4096  25169919  12582912  83 Linux
/dev/sda2       25169920 230690815 102760448  83 Linux
/dev/sda3      230690816 234441647   1875416  82 Linux swap / Solaris

# hdparm -Tt /dev/sda

Timing cached reads:   8938 MB in  2.00 seconds = 4470.88 MB/sec
Timing buffered disk reads: 826 MB in  3.00 seconds = 275.11 MB/sec

I think number should be higher and they were when disk was empty (~ 470 MB/sec for buffered disk reads) and even lower when system ran for several days (~ 120 MB/sec). EBS on all OCZ SSDs is 512Kb. To which sector should I align partitions to be aligned with EBS?

To allign to 512KiB you would allign to sector 1024 (512KiB= 524288 bytes / 512 (sector size) = 1024)