Mailinglist Archive: opensuse (933 mails)

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Re: [opensuse] openSUSE on SSD?
  • From: Roger Oberholtzer <roger@xxxxxx>
  • Date: Tue, 01 Jun 2010 10:10:03 +0200
  • Message-id: <1275379803.17165.85.camel@xxxxxxxxxxxx>
On Tue, 2010-06-01 at 09:06 +0200, Hans Witvliet wrote:
On Tue, 2010-06-01 at 08:09 +0200, Roger Oberholtzer wrote:
On Mon, 2010-05-31 at 23:32 +0200, Hans Witvliet wrote:

What about this stuff about aligning the disk blocks on a 4k boundary to
match the physical disk access? If that is not done when the disk is
formatted, there could be a performance penalty. I did not think
openSUSE did this.

you see things in the wrong perspective, imho.

For ages we use 512 byte blocks.
If you start using larger blocks you might gain some speed, but it
doesn't mean there is a performance penalty when using 512 byte blocks.

SSD disks do not use 4K blocks. Some have a 512k compatibility mode. But
that is buffering in the disk software - the physical access is 4K no
matter.

When doing a 20GB read, l get:
20480000000 bytes (20 GB) copied, 124.208 s, 165 MB/s
just a bit (185MB/s) faster when doing smaller transfers.
Good enough for a simple firewall, for me atleast...

What should i gain with 4K blocks?
I think this is more intended for ordinary drives with rotating
platters...

The disk cannot read/write 512K blocks. It must read/write 4K blocks.
Because of the way this works, if the disk has it's 4K blocks aligned
differently than the disk formatting, reading/writing can require more
accesses than necessary. I have been looking for an interesting article
I read recently about this. The effect was not huge, so it is not a show
stopper. But decreasing unnecessary disk access is usually not a bad
thing.

It seemed that the 'solution' was that the Linux disk formatting program
just had to be sure the logical 4k blocks align with the physical disk
blocks. The jury is out on which Linux distros do this. It is something
that must be done when the disk is formatted.

I do not know where openSUSE is on this. Is this something in 11.3?


--
Roger Oberholtzer

OPQ Systems / Ramböll RST

Ramböll Sverige AB
Krukmakargatan 21
P.O. Box 17009
SE-104 62 Stockholm, Sweden

Office: Int +46 10-615 60 20
Mobile: Int +46 70-815 1696

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