Linked by Thom Holwerda on Sun 18th May 2008 15:32 UTC, submitted by sjvn
Sun Solaris, OpenSolaris It seems like we're really on the subject of filesystems and related technology the past few days. We had an interview with the man behind BeServed, an item on WinFS' current status, and now we - possibly - have news on ZFS coming to Linux. Possibly, because it's all speculation from here on out.
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ZFS RAM requirements
by PlatformAgnostic on Sun 18th May 2008 22:48 UTC
PlatformAgnostic
Member since:
2006-01-02

When looking at the public information about ZFS (I can't read the source) from Sun blogs and other docs, I always wondered how they kept RAM requirements in check, because a log-structured filesystem has to keep a more-efficient block mapping structure in memory in order to get performance for common applications (the log by itself doesn't give you a good searchable structure). I figured it would be a little more expensive (maybe 2X) of a traditional filesystem. But needing a 2GB machine to use ZFS?? Yikes!

I guess it makes sense... Sun is a hardware company after all. While they lack all the fancy CoW and transactional features, at least the Linux filesystems and NTFS won't eat your machine.

Reply Score: 2

RE: ZFS RAM requirements
by jwwf on Sun 18th May 2008 23:48 in reply to "ZFS RAM requirements"
jwwf Member since:
2006-01-19

When looking at the public information about ZFS (I can't read the source) from Sun blogs and other docs, I always wondered how they kept RAM requirements in check, because a log-structured filesystem has to keep a more-efficient block mapping structure in memory in order to get performance for common applications (the log by itself doesn't give you a good searchable structure). I figured it would be a little more expensive (maybe 2X) of a traditional filesystem. But needing a 2GB machine to use ZFS?? Yikes!

I guess it makes sense... Sun is a hardware company after all. While they lack all the fancy CoW and transactional features, at least the Linux filesystems and NTFS won't eat your machine.


All of this talk reminds me of when NT 3.1 came out. People were aghast that it wanted something like 16 MB to perform well, back when that extra 8 MB was around $300. However, keeping in mind the horrors of 16 bit Windows, it was better to see MS try to do better even if they were a little ahead of the hardware curve. The hardware curve caught up and the investment paid off.

Reply Parent Score: 3

RE: ZFS RAM requirements
by phoenix on Mon 19th May 2008 03:17 in reply to "ZFS RAM requirements"
phoenix Member since:
2005-07-11

I figured it would be a little more expensive (maybe 2X) of a traditional filesystem. But needing a 2GB machine to use ZFS?? Yikes!


According to the ZFS Admin Manual (p. 41), you can use ZFS on [Open]Solaris with only 0.5 GB of RAM. They recommend a minimum of 1 GB, though, for the best performance (more is always better). Not sure where you get the "need 2 GB" meme. Even on FreeBSD 7, you only "need" 1 GB of RAM.

Reply Parent Score: 2

RE[2]: ZFS RAM requirements
by PlatformAgnostic on Mon 19th May 2008 08:47 in reply to "RE: ZFS RAM requirements"
PlatformAgnostic Member since:
2006-01-02

I was being hyperbolic... sorry.

Reply Parent Score: 2