Re: [zfs-discuss] Rule of Thumb for zfs server sizing with (192) 500 GB SATA disks?

[Richard Elling]

comment below...

William Papolis wrote:
 I checked this out at the Solaris internals link above, because I am also 
 interested in the best setup for ZFS.
 
 Assuming 500GB drives ...
 
 It turns out that the most cost effective option (meaning the least lost 
 drive space due to redundancy is to ...
 
 1. Setup RaidZ of up to 8 drives (All must be the SAME size; 8 x 500GB)
 2. Choose either 1 or 2 drives to be parity drives. (You lose this space)
 
 Bottom line is ...
 1. You have either 3.5TB or 3TB of space and (500 or 1TB for parity)
 2. with 500GB or 1TB devoted for redundancy. (for parity)
 3. You can simultaneously lose 1 or 2 drives and your ARRAY is still intact!
 
 This maximizes space and performance should be up there too, right? 
 How does this compare, performance wise, to 4 sets of 2-way mirrors?  (4 sets 
 of 2 -way mirrors is the fastest setup right? But you lose half the available 
 capacity!)
 
 Thanks,
 
 Bill
 
 HERE IS THE QUOTE FROM SOLARIS INTERNALS FOR SIZING AN ARRAY
 
 RAID-Z Configuration Requirements and Recommendations
 
 A RAID-Z configuration with N disks of size X with P parity disks can hold 
 approximately (N-P)*X bytes and can withstand P device(s) failing before data 
 integrity is compromised.
 
 * Start a single-parity RAID-Z (raidz) configuration at 3 disks (2+1)
 * Start a double-parity RAID-Z (raidz2) configuration at 5 disks (3+2)
 * (N+P) with P = 1 (raidz) or 2 (raidz2) and N equals 2, 4, or 8
 * The recommended number of disks per group is between 3 and 9. If you 
 have more disks, use multiple groups. 

As I read this, after two cups of coffee, it seems confusing.  The parity
disks will be part of the N for zpool create.

Cindy, let's try to make this more consistent with the actual commands for
managing pools.
  -- richard
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Re: [zfs-discuss] Rule of Thumb for zfs server sizing with (192) 500 GB SATA disks?

[Marc Bevand]

David Runyon david.runyon at sun.com writes:

 I'm trying to get maybe 200 MB/sec over NFS for large movie files (need

(I assume you meant 200 Mb/sec with a lower case b.)

 large capacity to hold all of them). Are there any rules of thumb on how 
 much RAM is needed to handle this (probably RAIDZ for all the disks) with
 zfs, and how large a server should be used ? 

If you have a handful of users streaming large movie files over NFS,
RAM is not going to be a bottleneck. One of my ultra low-end server
(Turion MT-37 2.0 GHz, 512 MB RAM, five 500-GB SATA disk in a raidz1,
consumer-grade Nvidia GbE NIC) running an old Nevada b55 install can
serve large files at about 650-670 Mb/sec over NFS. CPU is the
bottleneck at this level. The same box with a slightly better CPU
or a better NIC (with a less CPU-intensive driver that doesn't generate
45k interrupt/sec) would be capable of maxing out the GbE link.

-marc

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