Global hot spare for SAS Pool and SATA Pool?

[fips]

Hey guys,

I wanted to create a raidz2 with 8 SAS (1TB) disks and a raidz1 with 3 SATA (2TB) disks (for backup purposes).
Because I have a (SATA) slot free, I wanted to use this for a global hot spare 2TB SATA disk.

Is this possible?

Thanks in advanced
Steve

 

[Mirfster]

Technically "Yes". However, I would question a few things:

1. Are these vDevs (RaidZ2 & RaidZ1) in the same Volume/Pool?
   • If so, it generally is not a good idea to mix RaidZ levels...Especially where one vDev has less redundancy than another.
   • Loss of that vDev will cause total loss of the Volume/Pool regardless of the redundancy level(s) of the other vDevs
2. If they are NOT in the same Volume/Pool, then the answer is "No". As far as I understand spares are isolated to the Volume/Pool they are a member of. Willing to be corrected on this if I am wrong.

 

[fips]

Hi,
thanks for reply, well both raidZ doesn't exist yet.
I set up a new storage and have some free bays (but only with SATA connectors), so I thought how can I use them.

 

[Mirfster]

Hi,
thanks for reply, well both raidZ doesn't exist yet.
I set up a new storage and have some free bays (but only with SATA connectors), so I thought how can I use them.

Just to get clarity...

1. You have 8 x 1TB SAS Drives
2. You have 3 x 2TB SATA Drives
3. You have not setup any vDevs yet

So, do you have an HBA or another way to connect the SAS Drives? I ask because while SATA Drives can be connected to SAS Ports, SAS Drives cannot be connected to SATA Ports...

If you post your system specs (MB, CPU, RAM, HBA/Controllers, etc) then more info can be provided... As well, if you tell us what your envisioned "Use-Case" (Data, Plex Server, VM Storage, etc) is that would help as well...

 

[fips]

Just to get clarity...

1. You have 8 x 1TB SAS Drives
2. You have 3 x 2TB SATA Drives
3. You have not setup any vDevs yet

So, do you have an HBA or another way to connect the SAS Drives? I ask because while SATA Drives can be connected to SAS Ports, SAS Drives cannot be connected to SATA Ports...

If you post your system specs (MB, CPU, RAM, HBA/Controllers, etc) then more info can be provided... As well, if you tell us what your envisioned "Use-Case" (Data, Plex Server, VM Storage, etc) is that would help as well...

MB: Supermicro X10SL7-F with an LSI Onboard 8x SAS Controller.
CPU: Xeon E3-1220 (or something like this).
RAM: 16GB
I want a pool as a storage for KVM VMs.

I can install 8 SAS Disks and 4 SATA Disks, so I was just thinking what is the best solution.
I guess I will go for a 7 Disk Raidz3, seems that there is no better solution.

6 raidz2 = ok but what to do with my extra 1 sas disk?
7 raidz2 = not recommended
7 raidz3 = recommended
8 raidz2 = not recommended
8 raidz3 = not recommended too.

Sad, i like when everything (the disk bays) is full.

 

[Mirfster]

6 raidz2 = ok but what to do with my extra 1 sas disk?
7 raidz2 = not recommended
7 raidz3 = recommended
8 raidz2 = not recommended
8 raidz3 = not recommended too.

I think you have been misinformed... That is old thinking and does not pertain since FreeNAS 9.2.1. Nothing wrong at all with running a 7 or 8 disk wide RaidZ2 or RaidZ3...

For reference from the ZFS Primer:

Some older ZFS documentation recommends that a certain number of disks is needed for each type of RAIDZ in order to achieve optimal performance. On systems using LZ4 compression, which is the default for FreeNAS® 9.2.1 and higher, this is no longer true. See ZFS RAIDZ stripe width, or: How I Learned to Stop Worrying and Love RAIDZ for details.

 

[Stux]

You can use SATA disks with a SAS card

8 disk Raidz2 is fine, as is 7 disk.

Perhaps go with 2 vdevs of 6 disks each in raidz2

A hot spare is a waste of a disk, and also may cause data loss.

When you have a disk failure, it is better to refresh your backup and then use a warm spare to replace the failed disk, rather than immediately replace the failed disk, and possibly suffer another failure during the rebuild, before you've refreshed your backup.

 

[Mirfster]

Hey, just noticed that you asked a similar question back in 2014: "12 Drive: SAS and SATA Mix".. :P

Guess that endeavor never got completed? ;)

I'd agree with Stux as well as far as the usage of a Spare. If the Server has easy access, like near you then as long as you have a good vDev and notifications a spare is a waste. If the Server is off-site or somewhere not easily accessible then a spare can/should be considered.

 

[fips]

wow...good to know... Thanks!!!
So I will use 8 SAS disks, I will run some performance tests to see if raidz2 or raidz3.

Funny that if you are not inside for a couple of months you loose a lot of important infos, like a soap opera :D

 

[CraigD]

So I will use 8 SAS disks, I will run some performance tests to see if raidz2 or raidz3

Then run one more performance test with 4 SAS mirrors in a pool

Have Fun

 

[fips]

Then run one more performance test with 4 SAS mirrors in a pool

Have Fun

Maybe I am stupid, but I add via that drag web gui tool, a 4 SAS mirror raidz2, it was raidz2-0 and raidz2-1, performance was nothing better than raidz2 with 8 disk.
Now I deleted the pool, and created 4x Mirrors (always with "add extra Device") and hit add volume.
On screenshots you can see what was created. Is it a 4x mirror raidz2?

I can't see it.

 

[Mirfster]

Is it a 4x mirror raidz2?

It is 4 mirrors striped, not RaidZ2. Notice in the screen shots they say "mirror-0", "mirror-1", "mirror-2" and "mirror-3"? That is 4 mirrors. Wondering why it is called "Z2"? That name for the Pool/Volume is a little confusing, makes one think of RaidZ2... ;)

 

[fips]

Ok, once again

Is it now how it would be recommended?
It look for me like 2xraidZ2 mirrored.
I thought it would be better to have 4x mirrors and with this a raidz2?

 

[Mirfster]

That is two RaidZ2 vDevs (Not mirrored). At this stage I am not too sure what layout you actually want since you keep mixing up types of vDevs... lol.

I'm on my cell right now, anyone else know what the OP is looking to setup?

 

[nojohnny101]

maybe you could go back and tell use what your use case is like @Mirfster asked. this will help us determine what setup would be ideal.

If you need crazy performance and have a solid backup solution in place, then maybe just all mirrors in the same pool?

if you need some redundancy and are just doing standard stuff (shares [not too many users], couple of plugins, etc.) then I think best usage would be 2 x 6 disk raidz2 vdevs striped together.

 

[fips]

best usage would be 2 x 6 disk raidz2 vdevs striped together.

You can call me stupid, but this (2 x 4 disk raidz2 striped together) is what I would like to have.
But I cant configure it... :(

 

[gpsguy]

If that's what you want, you had it in post #13.

You can call me stupid, but this (2 x 4 disk raidz2 striped together) is what I would like to have.

 

[fips]

So now I created 5 different pools and ran performance tests.
IOMeter configured with default setup.
VM (2008r2) is on a proxmox Host connected via iSCSI.

Some other combination I can try?