[lustre-discuss] Avoiding system cache when using ssd pfl extent

John Bauer bauerj at iodoctors.com
Thu May 19 11:16:56 PDT 2022


No, not in  general.  It just seems that if one is storing data on an 
SSD it should be optional to have it not stored in memory ( why store in 
2 fast mediums ).

O_DIRECT is not of value as that would apply to all extents, whether on 
SSD on HDD.   O_DIRECT on Lustre has been problematic for me in the 
past, performance wise.


On 5/19/22 13:05, Patrick Farrell wrote:
> No, and I'm not sure I agree with you at first glance.
> Is this just generally an idea that data stored on SSD should not be 
> in RAM?  If so, there's no mechanism for that other than using direct I/O.
> -Patrick
> ------------------------------------------------------------------------
> *From:* lustre-discuss <lustre-discuss-bounces at lists.lustre.org> on 
> behalf of John Bauer <bauerj at iodoctors.com>
> *Sent:* Thursday, May 19, 2022 12:48 PM
> *To:* lustre-discuss at lists.lustre.org <lustre-discuss at lists.lustre.org>
> *Subject:* [lustre-discuss] Avoiding system cache when using ssd pfl 
> extent
> When using PFL, and using an SSD as the first extent, it seems it would
> be advantageous to not have that extent's file data consume memory in
> the client's system buffers.  It would be similar to using O_DIRECT, but
> on a per-extent basis.  Is there a mechanism for that already?
> Thanks,
> John
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