Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Chris Wedgwood
On Tue, Mar 13, 2007 at 01:11:44AM -0400, Andreas Dilger wrote: > I'd guess a vast majority of IO will have the end similarly > misaligned as the start. Very little filesystem IO is 512 bytes, > possibly excluding XFS in an unusual mode. XFS (mkfs.xfs) can be told what the native sector size is

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Andreas Dilger
On Mar 12, 2007 10:26 -0400, Jeff Garzik wrote: > In my own experiments on my own Fedora workstation, ~66% of IOs in Linux > start on an odd sector, and ~33% started on even-numbered sectors. For > a 1K-sector drive with 'odd' alignment, the configuration Microsoft will > likely want, that mea

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Bryan Henderson
>> I don't get this. If you mean partitions defined by the classic DOS >> partition table format, then AFAICS, such a partition can start in any >> sector. > >Only at "logical cylinder boundary" (except for the first partition). That's a requirement in ancient DOS systems that use CHS addre

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Jeff Garzik
Douglas Gilbert wrote: Bryan Henderson wrote: What is an odd-aligned disk? s/disk/partition/ ? Example: An odd-aligned disk in the 512-b logical / 1K-physical scenario is where odd LBAs indicate the start of a 1K physical sector. An even-aligned disk is where even LBAs indicate the start

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Douglas Gilbert
Bryan Henderson wrote: >> DOS partitions start partitions on odd-numbered sectors > > I don't get this. If you mean partitions defined by the classic DOS > partition table format, then AFAICS, such a partition can start in any > sector. Bryan, Typically the first partition on a DOS partitioned

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Sergei Shtylyov
Hello. Bryan Henderson wrote: DOS partitions start partitions on odd-numbered sectors I don't get this. If you mean partitions defined by the classic DOS partition table format, then AFAICS, such a partition can start in any sector. Only at "logical cylinder boudary" (except for the f

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Bryan Henderson
>DOS partitions start partitions on odd-numbered sectors I don't get this. If you mean partitions defined by the classic DOS partition table format, then AFAICS, such a partition can start in any sector. >so presuming you have odd-aligned disks, life is good. What is an odd-aligned disk? - T

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Martin K. Petersen
> "Doug" == Douglas Gilbert <[EMAIL PROTECTED]> writes: Doug> SAT is now a standard and an agenda item for SAT-2 is to wire Doug> ATA8-ACS's large sector size support to the additions to SBC-3 Doug> mentioned above. Doug> I'm not sure how this stuff plays with end to end data Doug> protection

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Douglas Gilbert
Ric Wheeler wrote: > Alan Cox wrote: >>> First generation of 1K sector drives will continue to use the same >>> 512-byte ATA sector size you are familiar with. A single 512-byte >>> write will cause the drive to perform a read-modify-write cycle. >>> This configuration is physical 1K sector, logi

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Christoph Hellwig
On Mon, Mar 12, 2007 at 10:45:16AM -0400, Jeff Garzik wrote: > Christoph Hellwig wrote: > >the occasional 2k sector SCSI MO device aswell. It would be nice to > >get samples of large sector size ATA devices into the hands of developers > >to do real world testing of the whole stack. > > "hands of

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Jeff Garzik
Christoph Hellwig wrote: the occasional 2k sector SCSI MO device aswell. It would be nice to get samples of large sector size ATA devices into the hands of developers to do real world testing of the whole stack. "hands of developers" meaning you specifically? :) I've had a 512b-logical/1K-ph

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Alan Cox
> For 1K/4K logical sector sizes, who knows. EFI? > Certainly seems incompatible with the current popular DOS partition format. Its a bit messier than that. There are two interpretations of "DOS" partition formats found on 2K sector size magneto opticals. One is that everything is the same as b

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread James Bottomley
On Mon, 2007-03-12 at 08:18 +, Christoph Hellwig wrote: > The FS stack and higher levels of the I/O stack should be mostly ready. > The S/390 DASDs are commonly used with 4k sector sizes, and we've had > the occasional 2k sector SCSI MO device aswell. It would be nice to > get samples of large

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Jeff Garzik
Jan Engelhardt wrote: On Mar 11 2007 22:45, Ric Wheeler wrote: Jan Engelhardt wrote: On Mar 11 2007 18:51, Ric Wheeler wrote: During the recent IO/FS workshop, we spoke briefly about the coming change to a 4k sector size for disks on linux. If I recall correctly, the general feeling was that

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Jeff Garzik
Jan Engelhardt wrote: On Mar 11 2007 18:51, Ric Wheeler wrote: During the recent IO/FS workshop, we spoke briefly about the coming change to a 4k sector size for disks on linux. If I recall correctly, the general feeling was that the impact was not significant since we already do most file syste

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Jeff Garzik
Alan Cox wrote: First generation of 1K sector drives will continue to use the same 512-byte ATA sector size you are familiar with. A single 512-byte write will cause the drive to perform a read-modify-write cycle. This configuration is physical 1K sector, logical 512b sector. The problem ca

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Ric Wheeler
Alan Cox wrote: First generation of 1K sector drives will continue to use the same 512-byte ATA sector size you are familiar with. A single 512-byte write will cause the drive to perform a read-modify-write cycle. This configuration is physical 1K sector, logical 512b sector. The problem ca

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Alan Cox
> First generation of 1K sector drives will continue to use the same > 512-byte ATA sector size you are familiar with. A single 512-byte write > will cause the drive to perform a read-modify-write cycle. This > configuration is physical 1K sector, logical 512b sector. The problem case is "rea

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Alan Cox
> Now, if this disk was copied byte per byte (/bin/dd) to a > 4096-based disk, and Linux would start using a sector size of > 4096, then I would suddenly have The ATA drives I'm aware of report 512 byte sector size, do 512 byte I/O's but use 4K physical sectors and to get sane performance except t

Re: impact of 4k sector size on the IO & FS stack

2007-03-12 Thread Christoph Hellwig
On Sun, Mar 11, 2007 at 06:51:53PM -0400, Ric Wheeler wrote: > > During the recent IO/FS workshop, we spoke briefly about the coming > change to a 4k sector size for disks on linux. If I recall correctly, > the general feeling was that the impact was not significant since we > already do most f

Re: impact of 4k sector size on the IO & FS stack

2007-03-11 Thread Andreas Dilger
On Mar 12, 2007 04:27 +0100, Jan Engelhardt wrote: > Assume this partition table on my current HD: > > Disk /dev/hdc: 251.0 GB, 251000193024 bytes > 255 heads, 63 sectors/track, 30515 cylinders > Units = cylinders of 16065 * 512 = 8225280 bytes > > Device Start

Re: impact of 4k sector size on the IO & FS stack

2007-03-11 Thread Jan Engelhardt
On Mar 11 2007 22:45, Ric Wheeler wrote: > Jan Engelhardt wrote: >> On Mar 11 2007 18:51, Ric Wheeler wrote: >> >> > During the recent IO/FS workshop, we spoke briefly about the >> > coming change to a 4k sector size for disks on linux. If I >> > recall correctly, the general feeling was that the

Re: impact of 4k sector size on the IO & FS stack

2007-03-11 Thread Ric Wheeler
Jan Engelhardt wrote: On Mar 11 2007 18:51, Ric Wheeler wrote: During the recent IO/FS workshop, we spoke briefly about the coming change to a 4k sector size for disks on linux. If I recall correctly, the general feeling was that the impact was not significant since we already do most file

Re: impact of 4k sector size on the IO & FS stack

2007-03-11 Thread Ric Wheeler
Alan Cox wrote: Are there other concerns in the IO or FS stack that we should bring up with vendors? I have been asked to summarize the impact of 4k sectors on linux for a disk vendor gathering and want to make sure that I put all of our linux specific items into that summary... We ne

Re: impact of 4k sector size on the IO & FS stack

2007-03-11 Thread Ric Wheeler
Jeff Garzik wrote: Alan Cox wrote: I would be interested to know what the disk vendors intend to use as their strategy when (with ATA) they have a 512 byte write from an older file system/setup into a 4K block. The case where errors magically appear Well, you have logical and physical secto

Re: impact of 4k sector size on the IO & FS stack

2007-03-11 Thread Jeff Garzik
Alan Cox wrote: I would be interested to know what the disk vendors intend to use as their strategy when (with ATA) they have a 512 byte write from an older file system/setup into a 4K block. The case where errors magically appear Well, you have logical and physical sector size changes. First

Re: impact of 4k sector size on the IO & FS stack

2007-03-11 Thread Jan Engelhardt
On Mar 11 2007 18:51, Ric Wheeler wrote: > > During the recent IO/FS workshop, we spoke briefly about the > coming change to a 4k sector size for disks on linux. If I > recall correctly, the general feeling was that the impact was > not significant since we already do most file system IO in 4k > p

Re: impact of 4k sector size on the IO & FS stack

2007-03-11 Thread Alan Cox
> Are there other concerns in the IO or FS stack that we should bring up > with vendors? I have been asked to summarize the impact of 4k sectors > on linux for a disk vendor gathering and want to make sure that I put > all of our linux specific items into that summary... We need to make sure

impact of 4k sector size on the IO & FS stack

2007-03-11 Thread Ric Wheeler
During the recent IO/FS workshop, we spoke briefly about the coming change to a 4k sector size for disks on linux. If I recall correctly, the general feeling was that the impact was not significant since we already do most file system IO in 4k page sizes and should be fine as long as we parti