Could support Raid 50 when use zfs filesystem?

[akong]

Hello,I don't know could freenas zfs filesystem have support raid 50 mode?Have any friend test it?

 

[danb35]

ZFS will support two (or three, or any number) of striped RAIDZ1 vdevs. It does not support RAID 0, 1, 5, 6, or any other numbered RAID configuration.

 

[akong]

What?
I can create mirror on my freenas use ZFS volume manager tool.Is it not support raid 1??

 

[anodos]

What?
I can create mirror on my freenas use ZFS volume manager tool.Is it not support raid 1??

Yes and no. ZFS is a file system and volume manager. Some of what it does is analogous to traditional RAID levels, but there are differences. A two way mirror is similar to RAID1, but you can also create three-way mirrors. I recommend reading the information here: http://doc.freenas.org/index.php/Hardware_Requirements#ZFS_Overview

To answer your original question: you can stripe vdevs. For instance, you can create two RAIDZ2 vdevs (similar to RAID6) and stripe them (creating something similar to RAID 60). This is probably the best way to do a large-scale increase of your storage capacity. For instance, if you have an 8-disk RAIDZ2 vdev and decide you need to grow your pool, the best way of doing this is to create a second 8-disk RAIDZ2 vdev and stripe the two vdevs.

For more information, check the documentation here: http://doc.freenas.org/index.php/Volumes#Extending_a_ZFS_Volume

 

[Ericloewe]

Because RAIDZ1/RAID5 is a bad idea, striped RAIDZ1 vdevs are an even worse idea.

Please read this document before asking further questions about disk configurations in FreeNAS:

http://forums.freenas.org/index.php...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/

 

[TFS_Rein]

RAIDZ2 is your better bet instead of raid 50 (stripped RAIDZ) this is because with Z2 you can loose ANY 2 disks. RAID50 you CAN loose two disks, but it depends on where the 2nd disk fails (same side of stripe =lost data or opposite = safe)

 

[danb35]

Some clarity on terms, please. ZFS does not use RAID 0, 1, 5, 6, etc. You're correct that a single 6-disk RAIDZ2 vdev will have better redundancy than two striped 3-disk RAIDZ1 vdevs, for the reason you state. However, performance will be worse. Whether that's an acceptable tradeoff is up to the user to determine.

 

[jgreco]

Whether that's an acceptable tradeoff is up to the user to determine.

Users typically don't have the real experience to evaluate the risk level correctly. RAIDZ1 is substantially risky due to a variety of factors, not the least of which is the rebuild time and lack of redundancy during that process. Putting two striped 3-disk RAIDZ1 vdevs online for "performance" reasons is mostly dumb; if you need performance then do three mirror vdevs and do it right in the first place. You gain a little more space with the 2 x 3-disk Z1's but at a significant performance dropoff. The risk model is also slightly safer with the mirror vdevs (if you lose a disk, you have a 1 in 5 chance that a second disk failure takes out the pool).

 

[panz]

Which is the risk level of a two RAIDZ2 pool? For example, is worth a conf with 12 disks, so the pool is striped in a 2x6 disks Vdevs, each Vdev = RAIDZ2?

 

[jgreco]

The difference above - frak, re-reading it I note that I failed to actually make it clear. The scenario above with the dual RAIDZ1's of three disks each means that if a disk fails, you then have a 2 in 5 chance that a second disk failing kills the pool. The striped mirror vdev scenario reduces that risk AND significantly improves performance, but offers less space.

Once we get up to RAIDZ2 the risk model is substantially mitigated because you still need two more failures at a minimum to lose. But let me answer the question I'd like you to think about a bit:

If you have 12 4TB drives in 2 x 6 x 4TB RAIDZ2, that gives you two 16TB vdevs or a 32TB pool with the ability to lose any two disks. You may be able to lose up to four disks as long as two are from each vdev.

I propose that an 11 device RAIDZ3 plus a warm spare may be a better alternative. It still gives you a 32TB pool but the ability to lose ANY three disks, PLUS the first time you lose a disk, there's a warm drive standing by for rebuild.

The downsides to RAIDZ3 are that RAIDZ3 performs more poorly than RAIDZ2, and definitely even moreso compared to a striped dual RAIDZ2 setup.

So the question needs to be, what's the goal? For archival storage, I really like the 12-drive RAIDZ3 (11 + spare). For performance, RAIDZ2 still isn't great and I'd probably rather go three way mirror. I'm not a real huge fan of the RAIDZ2 options as a result. If I had a 24 or 48 drive chassis and I needed the space and also better performance than Z3, then 6 disk Z2 vdevs would be definitely something to consider.