Mailing List Archive: Netapp: toasters

writes through NVRAM also in read cache?

Index | Next | Previous | View Threaded

tmerrill at mathworks

Nov 13, 2008, 9:09 AM

Post #1 of 3 (1062 views)
Permalink

*writes through NVRAM also* in read cache?**

While I'm thinking of it... During a conversation with my sales rep.,
this question came up... (Haven't had a chance to ask our local SE's
yet...)

If a write happens through NVRAM (which it always does), once the
write is acknowledged onto disk and the NVRAM flushed, is that data
in read cache *as well*? Or, is the path to disk for a write unique,
and when you want to read that data, it has to be read from disk
and *then* put into read cache?

I'm thinking of our software development environment, where we (of
course) do a lot of writing of object files and then linking them into
libraries and executables....

Until next time...

The MathWorks, Inc. 508-647-7000 x7792
3 Apple Hill Drive, Natick, MA 01760-2098 508-647-7001 FAX
tmerrill [at] mathworks http://www.mathworks.com
---

tmacmd at gmail

Nov 13, 2008, 9:29 AM

Post #2 of 3 (972 views)
Permalink

*Re: writes through NVRAM also* in read cache?** [In reply to]

If I recall correctly, "data" never officially comes from NVRAM.
That is just logging facilities.

The data comes in and immediately is logged into NVRAM *and* main memory.
The system just does not flush until 10sec or 1/2 full happens.
The blocks stay in main memory until they fall off the most recently used
queue.

As long as your requests come in and continuously access the data, it should
stay in RAM.

--tmac

RedHat Certified Engineer #804006984323821 (RHEL4)
RedHat Certified Engineer #805007643429572 (RHEL5)

Principal Consultant

On Thu, Nov 13, 2008 at 12:09 PM, Todd C. Merrill <tmerrill [at] mathworks>wrote:

>
>
> While I'm thinking of it... During a conversation with my sales rep.,
> this question came up... (Haven't had a chance to ask our local SE's
> yet...)
>
> If a write happens through NVRAM (which it always does), once the
> write is acknowledged onto disk and the NVRAM flushed, is that data
> in read cache *as well*? Or, is the path to disk for a write unique,
> and when you want to read that data, it has to be read from disk
> and *then* put into read cache?
>
> I'm thinking of our software development environment, where we (of
> course) do a lot of writing of object files and then linking them into
> libraries and executables....
>
> Until next time...
>
> The MathWorks, Inc. 508-647-7000 x7792
> 3 Apple Hill Drive, Natick, MA 01760-2098 508-647-7001 FAX
> tmerrill [at] mathworks http://www.mathworks.com
> ---
>
>

Chris.Blackmor at amd

Nov 13, 2008, 10:07 AM

Post #3 of 3 (978 views)
Permalink

*Re: writes through NVRAM also* in read cache?** [In reply to]

Writes are also put into read cache. If you have a highly cache dependent file system on a filer with high writes you are also caching those and will roll what is in cache more.

We ended up moving our tools repos to low write filers to alleviate the problems we were experiencing from this.
C-

----- Original Message -----
From: owner-toasters [at] mathworks <owner-toasters [at] mathworks>
To: toasters [at] mathworks <toasters [at] mathworks>
Sent: Thu Nov 13 11:09:05 2008
Subject: writes through NVRAM *also* in read cache?

While I'm thinking of it... During a conversation with my sales rep.,
this question came up... (Haven't had a chance to ask our local SE's
yet...)

If a write happens through NVRAM (which it always does), once the
write is acknowledged onto disk and the NVRAM flushed, is that data
in read cache *as well*? Or, is the path to disk for a write unique,
and when you want to read that data, it has to be read from disk
and *then* put into read cache?

I'm thinking of our software development environment, where we (of
course) do a lot of writing of object files and then linking them into
libraries and executables....

Until next time...

The MathWorks, Inc. 508-647-7000 x7792
3 Apple Hill Drive, Natick, MA 01760-2098 508-647-7001 FAX
tmerrill [at] mathworks http://www.mathworks.com
---

Index | Next | Previous | View Threaded

Interested in having your list archived? Contact Gossamer Threads