Messages in this thread | | | Subject | Re: ATA support for 4k sector size | From | "Martin K. Petersen" <> | Date | Wed, 25 Feb 2009 19:04:41 -0500 |
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>>>>> "david" == david <david@lang.hm> writes:
>> 512-byte logical / 512-byte hardware (current) 512-byte logical / >> 4096-byte hardware (ATA, doing read-modify-write) 4096-byte logical / >> 4096-byte hardware (SCSI initially, ATA later)
david> add to this good support for SSDs
david> ?? logical / 128K hardware
david> or similar.
Yep. And that goes for RAID arrays too.
For SCSI there some knobs we can query to get this information and my alignment changes are using those (and they are in turn what Willy's stuff hooks into).
I've been lobbying the SSD vendors whose architecture is prone to misalignment problems to propose a similar set of knobs for ATA. But so far it's just been a lot of talking.
My topology changes are a bit abstract in the sense that they expose:
- smallest I/O you can submit without incurring a penalty (hw sector, raid chunk size)
- optimal I/O size for the device in question
- biggest I/O you can submit without incurring a penalty
- alignment
We can use these parameters to lay out partitions and filesystems optimally. Just like we currently do with XFS but implemented in a more generic way that all filesystems can use.
-- Martin K. Petersen Oracle Linux Engineering
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