Software SSD Cache Implementation For Linux? 297
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?"
Re:I don't get it (Score:5, Insightful)
so
CPU L1
CPU L2
CPU L3
RAM
SSD
DISK
NETWORK
Internet
I estimate SSDs would be closer to Level 5 cache.
Re:Counter-Productive (Score:3, 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.
Re:isn't 40 GB enough for applications? (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...
Re:Thread summary (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.)