Which CPU for fastest write speed in RAIDZ3?

[FrankenServer]

I am planning to build a backup server for my primary computer, no other computers will be connected and it will not be used for real-time data access.

I want the backup/restore operations to take as little time as possible, with the disks being the only limiting factors.

So assuming that the latest HDDs operate at roughly 200MB/s, what processor(s) can calculate parity for three of them without becoming a bottleneck?


(Also I am aware that gigabit ethernet maxes out at 125 MB/s, I plan to use a pair of crossover cables to compensate.)

[raulfg3]

actually your real botleneck is you LAN/NIC .

Link agregation do not work as you espected ( do not double banwith for only one file/ PC at time), is really usefull for a small SOHO with several PC accessing to server at same time.

http://wiki.nas4free.org/doku.php?id=do ... d_failover

viewtopic.php?f=58&t=6921
viewtopic.php?f=58&t=5963

[b0ssman]

you could think about using intel X540-T1 cards in a crossover configuration.

as for cpu. the faster the better. since you have to go with a xeon processor anyway the E3-1271V3 will do very well.

[apollo567]

E3-1271V3

Do you really think you have to go as far for a NAS, even if there are high demands for performance ??

[b0ssman]

when using 10 gbit network cards yes.

the samba process is going to be the limiting factor.

[FrankenServer]

actually your real botleneck is you LAN/NIC .

Link agregation do not work as you espected ( do not double banwith for only one file/ PC at time), is really usefull for a small SOHO with several PC accessing to server at same time.

Your last link's comparison to a multi-core CPU was very helpful, but is there no way to make the backup's transmission 'multithreaded' to take advantage of the extra lane(s)?

Also, it occurred to me that I might run into trouble getting a matching link set up in Windows...

when using 10 gbit network cards yes.

the samba process is going to be the limiting factor.

What would the Samba process' maximum throughput be in a 4 GHz CPU, and how might it compare to parity calculation's limit factor?

[raulfg3]

CPU for parity is not a limiting factor, you can search in google for some test & articles:

https://calomel.org/zfs_raid_speed_capacity.html
http://www.anandtech.com/show/3963/zfs- ... marking/11
http://www.csamuel.org/2007/01/01/zfs-d ... and-raid-z

CPU for SAMBA transfer is a limiting factor.

[b0ssman]

you cant just say run multithreaded and lacp now uses the entire bandwidth.

it depends on which port you are using.

lacp calculates a hash from source,destination, port. all traffic in that combination will go through the same nic.
so even if you run it multithreaded, it does not guarantee that it will use both nics.

[FrankenServer]

Let's say I stay with a gigabit Ethernet connection between two Intel controllers in crossover, how many cores should the CPU have and what speed should they run at to keep up with RAIDZ3 and Samba at the full theoretical 125 megabytes per second?

Also, since that's all I'd be wanting the machine to handle, would the amount of processor cache matter at all?

[b0ssman]

cifs has a lot of overhead. so you are looking at around 100mb/sec transfer.

an haswell pentium should be able to achieve that.

[FrankenServer]

cifs has a lot of overhead. so you are looking at around 100mb/sec transfer.

an haswell pentium should be able to achieve that.

Will this Haswell Xeon possibly be able to exceed 100mb/sec?

http://ark.intel.com/products/75052/Int ... e-3_10-GHz


If not what ECC model(s) might be able to saturate Ethernet's bandwidth?

[b0ssman]

around 100mb/sec is the max you are gonna get out of gigabit ethernet.
you will never achieve 125 megabytes/sec

[FrankenServer]

around 100mb/sec is the max you are gonna get out of gigabit ethernet.
you will never achieve 125 megabytes/sec

Oh, okay then.

Thank you very much for your help, guys.

[FrankenServer]

cifs has a lot of overhead. so you are looking at around 100mb/sec transfer.

an haswell pentium should be able to achieve that.

Will a 3GHz dual-core be enough to handle RZ3, Samba, and all the background stuff at the same time, or should I get a quad-core?

And what about L3 cache size, would there be a noticeable difference between 2 and 8 megabytes at 3 GHz?

[b0ssman]

depends on what this "all the background stuff" is.

parity yes

[FrankenServer]

depends on what this "all the background stuff" is.

parity yes

Well parity is a convincing reason to get a quad-core for the extra cache, but I'm still curious: I'm not too familiar with the background processes of NAS4Free, but assuming Its only purpose would be to back up a Windows computer to a RaidZ3 array over Samba, would the server benefit from having more than 2 cores?

[b0ssman]

unfortunately zfs does not have such a nice output like the linux kernel

this should give you an idea what we are talking in terms of parity calculation.

http://pastebin.ca/2515041

[ 0.123609] smpboot: CPU0: Intel(R) Core(TM) i5-3570K CPU @ 3.40GHz (fam: 06, model: 3a, stepping: 09)

[ 1.764751] raid6: using algorithm sse2x4 (14262 MB/s)