10x3TB RAIDZ2 + 1 spare or 11x3TB RAIDZ3

[Quba]

I have 11 disks 3TB Hitachi Ultrastar 7K4000. I am creating storage for backup of data of 30 people. Internet connection is 1Gbs, so I do not need fast storage because ethernet speed is limiting factor and I do not expect it will be better.

I am thinking about 10x3TB RAIDZ2 + 1 spare or 11x3TB RAIDZ3 and I cannot decide which solution is better (safer). I suppose that both offer approximately the same speed. I am able to buy new drive in 3-4 days.

Thanks for any advice or discussion about it (use of spares).

 

[Mirfster]

First off, if you have not done so, I would recommend taking a look at Cyberjock's or Dlavigne's guides:

https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/
https://forums.freenas.org/index.php?threads/zfs-primer.38927/

For me personally, I would go with the RAIDZ2 since it is the safest. If it were possible to have 12 disks, then using 2 vdevs of 6x3TB RAIDZ2 would be preferred. Reasoning for this is that with a smaller vdev set, you could then increase the size by only having to upgrade the disks in one vdev at a time as opposed to having to upgrade all at one time.

There is always some sort of "trade off" between total usable space, speed and redundancy. At the end of the day it is better to have a good understanding before "pulling the trigger".

From a basic standpoint, using 11 disks in a vdev is pretty much the maximum recommended and you would not really want to go any higher. RAIDZ2 offers the most protection, while RAIDZ3 offers faster performance with a little lesser protection.

As far as the 1GB Internet Speed, I am assuming that you mean that is your network (LAN) speed and not how fast you are connected to Internet (otherwise I would be very jealous). That should be fine and is pretty much the standard speed.

If you could post information on the chassis/system then more feedback may be possible.

 

[Mirfster]

Oh as far as spares go; if the Server is "off site" and not easily accessible (say in a data center of something) then I would recommend considering spares. But, if it is "on site" and physically easily accessible (in the office or data center in same building) than I am not a big fan of using spares.

To me if I can get to it and replace a failed drive without too much hassle it is better to not use a spare and have that drive actually being used instead of just sitting there waiting to be used. Especially if I am using RAIDZ2; since each vdev can lose up to two drives without data loss.

 

[gpsguy]

Were you thinking RAIDz1 instead of RAIDz3? RAIDz3 offers more protection than RAIDz2 and will be a little slower.

RAIDZ2 offers the most protection, while RAIDZ3 offers faster performance with a little lesser protection.

 

[Mirfster]

Were you thinking RAIDz1 instead of RAIDz3? RAIDz3 offers more protection than RAIDz2 and will be a little slower.

Thanks for catching that. Guess my coffee hadn't kicked in yet. Actually what I wanted to state was that RAIDZ3 offers the most protection, while RAIDZ2 offers faster performance with a little lesser protection.

 

[Quba]

Thanks for all replies.

I have read both articles about ZFS.

Server will be on LAN in server room, so easilly accessible to change failed disk (but I know that failure appears when I will be on hollidays or something like that).

I started to think aboud 2 vdevs 6x3TB RAIDZ2 instead of 11x3TB RAIDZ3, even if I think there will be no need to increase storage capacity (because backup server of this server should be also upgraded).

The hardware will be: Supermicro MBS X10SLL-F-B, 32 GB ECC RAM, LSI SAS9211-8i