NAS and RAID Terms

[BobCochran]

Hi,

I am new to NAS and RAID and feel the need of some help with the terms I see people use in the forums. For example:

vdev
mirror
stripes ("stripes across them")
spindle ("2x 5 spindle")

I am actively reading the 8.0.3 manual, and I surf these forums a lot reading different posts to help with my education. With that said:

What is the difference between a vdev, a stripe, a spindle, and a hard drive? I'm not sure of the definitions here.

What is meant by "striping across them" when talking about adding hard drives.

When a "2x 5 spindle" is suggested, what does that mean?

Is there a book and/or website I should be reading for basics like this?

Thanks

Bob

 

[louisk]

...
vdev
mirror
stripes ("stripes across them")
spindle ("2x 5 spindle")

I am actively reading the 8.0.3 manual, and I surf these forums a lot reading different posts to help with my education. With that said:

What is the difference between a vdev, a stripe, a spindle, and a hard drive? I'm not sure of the definitions here.

What is meant by "striping across them" when talking about adding hard drives.

When a "2x 5 spindle" is suggested, what does that mean?

vdev is a virtual device. I believe that Sun coined the term when they released ZFS. It describes one or more physical drives in a pre-defined configuration.

mirror is a term for RAID1, where you have a pair of drives that have exactly the same data on them, and they operate as 1 drive.

stripe is when you take a chunk (say 32k) and write to a sequence of disks instead of writing to a single disk. each disk gets 32k.

spindle is another name for spinning disk (as opposed to flash/ssd)

Much of this would be detailed in ZFS documentation and/or wikipedia under RAID

 

[kbarb]

@BobCochran . . . lol - I feel the same way, perhaps. I started out trying to make a little shoebox home server w/ Freenas7, just about got it set up with UFS, then when I finally got back to the project, Freenas8 had come out. Everyone says to use ZFS - (how bad can that be) - now I find myself having fallen into "pools", "tanks", vdevs, slices and so on. Was trying to have a life. ;-)

As noted, you can find out a lot on Wikipedia's page for ZFS - a really compelling page-turner that I would advise anyone take with them on vacation. ;-)
http://en.wikipedia.org/wiki/ZFS
Wikipedia also for RAID, etc.
I haven't found a page yet on ZFS for noobs but it probably exists.

 

[survive]

Hi guys,

If you are interested on ZFS watch this:

https://blogs.oracle.com/video/entry/becoming_a_zfs_ninja

-Will

 

[BobCochran]

Louis and Kbarb,

Thank you so much for your help! I will read the suggested pages. And thanks for explaining some of the terms. I have a lot to learn here, especially about ZFS.

Bob

 

[jgreco]

spindle is another name for spinning disk (as opposed to flash/ssd)

Spindle is a term primarily used by people concerned with performance; it used to be that for parallelism, you would use lots of spindles, meaning lots of independent sets of heads, meaning more I/O could be happening in parallel. Many of the people who use the term now store their data on SSD. However, I have not really noticed that people do NOT refer to SSD's as spindles ... in an array of SSD's, some people still term them as such. It is just that there's much less advantage to multiple spindles with SSD, so those of us who have arrays of them typically just have two sufficiently large units mirrored, rather than dozens of hard drives or whatever. While the term comes from the legacy hardware name for the spinning hub of a hard drive, the term seems to have grown in meaning to mean "a discrete storage drive of some sort", much in the same way that a "cable modem" isn't really a modem. Just a terminology warning. It'll be fun when people start calling hybrid disks SSD's. Oh, wait, that's happened already, too. :-(