4 Drives - 2 Volumes - 2 Mirrors?

[HenryHonda]

Newbie question - maybe totally stupid - please be gentle...

About to take delivery of TS-453 pro. Rather than go for RAID 10, can I set two disks up as separate volumes and then mirror them to other two disks? In other words, avoiding the striping which will be the case with RAID 10. System will be backed-up to external USB 3.0 drive.

Why 2x RAID 1? - to get large storage capacity without using recent 6TB drives with unknown reliability.

As I said, all of this may be complete failure in my reasoning...

 

[thiggins]

So you want to create two RAID1 volumes? Sure you can do it. The main downsides are lower total capacity and the need to manage storage in two volumes.

Using 2TB drives as an example, either your scheme or RAID10 yields 4TB total storage. Using RAID5 yields 6TB.

 

[HenryHonda]

Thanks Tim,

Yes I realise that RAID 10 or 2x RAID 1 is inefficient capacity-wise, but I've read so much about the limitations of RAID 5, and that it is 'inappropriate' for small NASs, that I was tending to the ultra-cautious configurations.

I've ordered 4x WD Red 3TB (EFRX), giving a max capacity of 6TB in the more inefficient configurations. RAID 10 is tempting due to speed advantages from striping - but I don't know how much of a hassle it would be in the event of a single disk failure and subsequent rebuild.

As I said, scheduled backups to an external USB 3.0 drive is planned.

I obviously have to do a lot more reading...

 

[azazel1024]

For a NAS that is connected over GbE link, RAID0 or RAID10 isn't going to get you much performance unless you are hitting it with rather small files.

Those drivers in RAID1/single disk are already going to saturate a Gigabit connection (~115-118MB/sec) unless they are quite full.

I only RAID0, because I have more than a single GbE link, I've got 2Gbps between my desktop and server (Thank you SMB Multichannel)*. That said...I used to have RAID0, down to only a single disk in both machines, for now. Once I can afford to, I'll rebuild RAID0 arrays on both machines so that I have 2x3TB drives instead of the 1x3TB I have now (I used to have 2x2TB and 2x1TB, but a 2TB started to give me some concerns and my 2x1TB was out of capacity (less than 10% free)).

*That also said, even with the Seagate 3TB 7200rpm drives in a single drive configuration, between OS caching and generally good drive performance, I typically get 150-180MB/sec between the machines and often enough get 210-230MB/sec (it maxes/maxed at 235MB/sec when I had the RAID0 configuration before). I guess some advantages to 8GB of RAM on my server and 16GB of RAM on my desktop. Still itching to have 2x3TB RAID0 setup so that I hit 235MB/sec and stay there all day long.

 

[HenryHonda]

Thanks mate,

Yes, I only have a 1GbE network at the moment but, being a total newbie, I had no feel at all for how much a mirror configuration would limit transfer rates. It appears not very much...?

I've also ordered a pair of 4GB Kingston DDR3L RAM sticks to max the RAM to 8GB.

As I've said, I'm feeling my way very carefully at the moment, but have certainly over-specified the kit I'm buying - in the hope that I can make much better use of it as I climb the steep learning curve.

Apart from doing scheduled backups of a desktop (ethernet) two laptops (WiFi) and two android tablets (WiFi), I will be streaming full HD Blu-ray rips to a media player (Dune HD Smart D1 - ethernet) connected to my Panasonic plasma via my Denon AV receiver.

Cheers

 

[stevech]

I chose to NOT use a literal mirror (like RAID1) becuase that takes away protection from file system corruption or accidental file deletion.
Instead, I use two volumes, two file systems.

The RAID1 mirror would just duplicate the screw-up.

 

[azazel1024]

I chose to NOT use a literal mirror (like RAID1) becuase that takes away protection from file system corruption or accidental file deletion.
Instead, I use two volumes, two file systems.

The RAID1 mirror would just duplicate the screw-up.

My personal choice too. If possible I'd set it up as two JBOD volumes and then backup one volume to another, instead of using RAID1.

 

[stevech]

Few realize that

The RAID1 mirror would just duplicate the (hosed file system) or human error screw-up.

Two volumes. Separate file systems. Even in a 2 bay.
And robust automated backups to external media.