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freenas of linux

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Oct 31, 2012
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Guys I have some concerns about putting together a file server. First off I will be converting one of our existing systems to perform this task the box has 8 gigs of ram the cpu is a core 2 duo 1.86 and the raid controler is an IBM M1015. I will be using either Centos or Freenas the requirements are that whatever I do the box will need to be able to serve up smb and I want active directory integration also most likely I will play around with a little iscsi for testing variuos clusters such as Exchange or Sql Server. Now if I go with Freenas do you guys recommend UFS or ZFS I will have around 12 to 15 terabytes worth of storage in this system if I go Linux what file system would you recommend and how would I do the active diretory integration? I have heard that ZFS is a ram hog and you need a gig of ram terabyte also I read that Freenas requires 2 gigs of ram just for AD integration anyway let me know what you all think.
 
ZFS can utilise RAM more effectively than other filesystems. That's not a weakness, it's a strength. ZFS separates most recently accessed filecache and most frequently requested filecache. Old fashioned filesystems use a very simple cache which only caches last accessed data.

UFS or NTFS or Ext4 just as easily consume hundreds of gigabytes of RAM if you had that much amount of RAM. In fact, any modern system should have about 80% of its RAM dedicated to filecache. Only a fraction of the RAM is used by applications. This is normal and intended how modern computing works. RAM is your cache-layer between the CPU and disk.

Choosing between UFS or ZFS is rather easy. Do you care about your data? Do you want to give real protection to your data? No? Then use UFS/NTFS/Ext4. :)
 
I see what you are saying about ZFS and I have no problems with it but the system I have maxes at 8 gigs of ram. I was looking on the ZFS wiki and according to them you are supposed to have 1 gig of ram per terabyte I will have at least 15 TB's worth of data that's why I was ruling zfs out.
 
I'm running 20TB on 4gb of ram. it still works, its just not ideal. if its just a file system you can get away with less, if you're running a bunch of VM's, it would hurt performance some.
 
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Well right now I'm undecided I was going to make it just for serving files than again I thought about adding 4 more sata drives that would be running esxi vm's. So basically it sounds like if I do nothing but serve files it will be ok but don't try to run vm's.
 
8GB is good since this is more than 4GB which is the limit at which prefetching is disabled on BSD platforms - though not on Solaris platforms.

The rule of thumb '1GB per 1TB' is incorrect. You need more memory to unlock higher speeds. So 1GB per 100MB/s of performance would be slightly more accurate. You do not need more RAM as the capacity of the array grows, but rather more RAM to utilise more of the performance potential your disks offer.

With insufficient RAM, you will simply have lower performance than you could have had. So I would stick to your 8GiB setup but do not consider this to be any problem if you want to run ZFS.

Do be aware that 8GiB is on the low side. If you do things like L2ARC cache this also consumes RAM. Then you could get into trouble. But a simple L2ARC of 10GB would be okay.
 
I want performance at least equal to my current Dell Perc 5i card I normally can write to the 5 Samsung 2tb drives at 115MB.
 
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