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Software SSD Cache Implementation For Linux?

Posted by timothy on from the only-obscure-if-you-think-it-is dept.

Annirak writes "With the bottom dropping out of the magnetic disk market and SSD prices still over $3/GB, I want to know if there is a way to to get the best of both worlds. Ideally, a caching algorithm would store frequently used sectors, or sectors used during boot or application launches (hot sectors), to the SSD. Adaptec has a firmware implementation of this concept, called MaxIQ, but this is only for use on their RAID controllers and only works with their special, even more expensive, SSD. Silverstone recently released a device which does this for a single disk, but it is limited: it caches the first part of the magnetic disk, up to the size of the SSD, rather than caching frequently used sectors. The FS-Cache implementation in recent Linux kernels seems to be primarily intended for use in NFS and AFS, without much provision for speeding up local filesystems. Is there a way to use an SSD to act as a hot sector cache for a magnetic disk under Linux?"

4 of 297 comments (clear)

  1. Re:I don't get it by Colin+Smith · · Score: 4, Insightful

    so

    CPU L1
    CPU L2
    CPU L3
    RAM
    SSD
    DISK
    NETWORK
    Internet

    I estimate SSDs would be closer to Level 5 cache.

     

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  2. Re:Counter-Productive by Unit3 · · Score: 2, Insightful

    Define "unnecessarily". Given current SSD costs and depletion rates, it's probably completely acceptable to replace an SSD used as an intermediary cache in front of a large spindle-based array every couple of years.

    Just because it's not useful to you, doesn't mean it's not useful.

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    -- sudo.ca
  3. Re:isn't 40 GB enough for applications? by kgo · · Score: 2, Insightful

    Yeah, but if you've got some 'enterprise-level database' with those sort of transaction requirements, you can probably justify the purchase of SSDs. It's not exactly like you're building that system from craigslist parts...

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    Can you construct some sort of rudimentary lathe?
  4. Re:Thread summary by EvanED · · Score: 2, Insightful

    No kidding. It's threads like this (where I think the question is entirely reasonable and a good thing to support) that really sour my opinion of Linux. There are a few other things -- better file-system-supported metadata, transactional filesystems, etc. -- that have come up in the past too where it seems I just flat out disagree with most hardcore Linux users.

    (Don't worry, I hate Windows too, but for mostly different reasons. I don't use OS X very often and don't have an opinion on it, but I'd probably hate it too.)