Re: 20TB Storage System (fsck????)

From: Terry Lambert (tlambert2_at_mindspring.com)
Date: 09/04/03

  • Next message: Geoff Buckingham: "Re: 20TB Storage System (fsck????)" 
    Date: Thu, 04 Sep 2003 01:12:45 -0700
To: Max Clark <max.clark@media.net>

    Max Clark wrote:
    > Ohh, that's an interesting snag. I was under the impression that 5.x w/ PAE
    > could address more than 4GB of Ram.

    The kernel being able to address the RAM does not meant that
    the KVA+UVA space is larger than 4G. At best, you could take
    the uiomove/copyin/copyout performance hit, and move both of
    thse to 4G, each, rather than 4G total. That still limits you
    to 4G.

    > If fsck requires 700K for each 1GB of Disk, we are talking about 7GB of Ram
    > for 10TB of disk. Is this correct? Will PAE not function correctly to give
    > me 8GB of Ram? To check 10TB of disk?

    No, it will not.

    > Is there anyway to bypass this requirement and split fsck into smaller
    > chunks? Being able to fsck my disk is kinda important.

    Yes. Limit the number of CG bitmaps you examine simultaneously,
    and make the operation multiple pass over the disk. This is not
    that hard a modification to fsck, and it can be done fairly
    quickly by anyone who understands the code. The code in time to
    fsck the disk will go up inversely proportionally to the amount
    of RAM it's allowed to use, which is limited to the UVA size
    minus the fsck program size itself, and the fsck buffers used for
    things like FS metadata for a given file/directory.

    > I have zero experience with either itanium or opteron. What is the current
    > status of support for these processors in FreeBSD? What would the preferred
    > CPU be? Will there be PCI cards that I would not be able to use in either of
    > these systems?

    I have no idea whether these systems support a larger UVA size,
    or how much memory you could jam into them...

    -- Terry
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  • Next message: Geoff Buckingham: "Re: 20TB Storage System (fsck????)"

    Relevant Pages

    • RE: 20TB Storage System (fsck????)
      ... I was under the impression that 5.x w/ PAE ... could address more than 4GB of Ram. ... To check 10TB of disk? ... status of support for these processors in FreeBSD? ...
      (freebsd-hackers)
    • RE: 20TB Storage System (fsck????)
      ... I was under the impression that 5.x w/ PAE ... could address more than 4GB of Ram. ... To check 10TB of disk? ... status of support for these processors in FreeBSD? ...
      (freebsd-performance)
    • Re: 20TB Storage System (fsck????)
      ... I was under the impression that 5.x w/ PAE ... > could address more than 4GB of Ram. ... Being able to fsck my disk is kinda important. ... Is it possible for you to break up the 10TB partitions into 4TB ...
      (freebsd-hackers)
    • Re: 20TB Storage System (fsck????)
      ... I was under the impression that 5.x w/ PAE ... > could address more than 4GB of Ram. ... Being able to fsck my disk is kinda important. ... Is it possible for you to break up the 10TB partitions into 4TB ...
      (freebsd-performance)
    • Re: 20TB Storage System (fsck????)
      ... I was under the impression that 5.x w/ PAE ... > could address more than 4GB of Ram. ... Being able to fsck my disk is kinda important. ...
      (freebsd-hackers)