[wplug] Help deciding a RAID+LVM+LUKS setup

[Justin Smith]

> I  Get a second 2TB drive and 4TB drive;
>     1 If the 2TB drive you have is not under LVM,
>       A Add  4TB to system, setup as a 4TB LV under LVM but do not MAX 
out
>          and copy present 2 TB to it, after verifying data
>       B Move old 2TB to LVM in same VG,
>       C Add new 2TB drive in same VG,
>       D Setup mirror (RAID 1) of the two 2TB drives to 4TB LV,
>          the two 2TBs free space may be less or more than on the 4GB LV
>          but once mirrored can be increased to the smaller of the two.
>       E Extend ext 3/4 file-system to size of LVs
>         (You can move to the below configuration if you get a 2nd 4TB drive
> later)

That’s just the sort of solution I was looking for, Greg! It’s safer than RAID 
5, not as costly as RAID 10, and more flexible with future expansion. I even 
found a step-by-step LVM + LUKS + RAID 1 guide for my favorite distro: 
/http://jasonwryan.com/blog/2012/02/11/lvm//[1]

Pat and Drew, I appreciate hearing your accounts of RAID 5, but I think I’m 
going to play it safe this time. The theory I’ve heard about RAID 5 goes 
something like this: SATA hard disks have an unrecoverable read error 
(URE) rate of one per ~12 TB. Therefore, large arrays are more likely to 
experience them. If a disk in a RAID 5 array fails and any of the remaining 
disks throws a URE, the entire array fails.

And yes, it may seem a little “extreme” to go for full-disk encryption on a 
home server, but in light of recent events, encryption is about all we have 
at our disposal to do something about the surveillance state. 

LVM and different levels of RAID are new to me but very, very interesting. 
Out of curiosity, did any of you ever “short stroke” RAID 0 hard drives? It’s 
an arrangement that only uses the outermost (fastest) part of each 
platter. In years gone by, that was all the rage among gamers - that and n-
key rollover, courtesy of a well-designed mechanical keyboard.

--
*Justin S. Smith*
Vice chair/secretary, WPLUG Board of Directors
http://www.wplug.org[2] 

/"Isn't it ironic that the proprietary software developers call us 
communists? We are the ones who have provided for a free market, where 
they allow only monopoly."/
-Richard Stallman


> Justin,
> 
> With a 2TB drive already, I would go one of two ways with LVM using RAID 
1.
> 
> I  Get a second 2TB drive and 4TB drive;
>     1 If the 2TB drive you have is not under LVM,
>       A Add  4TB to system, setup as a 4TB LV under LVM but do not MAX 
out
>          and copy present 2 TB to it, after verifying data
>       B Move old 2TB to LVM in same VG,
>       C Add new 2TB drive in same VG,
>       D Setup mirror (RAID 1) of the two 2TB drives to 4TB LV,
>          the two 2TBs free space may be less or more than on the 4GB LV
>          but once mirrored can be increased to the smaller of the two.
>       E Extend ext 3/4 file-system to size of LVs
>         (You can move to the below configuration if you get a 2nd 4TB drive
> later)
 
> II Get a second 2TB drive and two other drives of same size (two 2TBs, 
3TB
> or 4TBs);
 1 If the 2TB drive you have is not under LVM,
>       A Add new 2TB to system, setup as a 2TB LV under LVM
>          and copy present 2TB to it, after verifying data
>       B Move old 2TB to LVM in same VG,
>       C Setup mirror (RAID 1) of the two 2TB LVs
>       D Add 2nd pair of new drives to same VG
>       E Extend LVs of the original LVs to new LVs.
>       F Extend ext 3/4 file-system to size of LVs
> 
> Greg
> 
> -----Original Message-----
> From: wplug-bounces+alheidgj=upmc.edu at wplug.org
> [mailto:wplug-bounces+alheidgj=upmc.edu at wplug.org] On Behalf Of 
Justin
> Smith
 Sent: Sunday, July 21, 2013 11:31 PM
> To: wplug at wplug.org
> Subject: [wplug] Help deciding a RAID+LVM+LUKS setup
> 
> Anyone who’s met me in person knows that I take great pride in my little
> CentOS server. I built it last fall when I got the itch to start running my
> own
 services. Before I knew it, I was using the server for a file server
> as well, and the space has really filled up. A single 2 TB drive only gets
> you so far, you know?
> 
> I need to expand the storage, and I’ve heard that LVM pairs well with 
RAID.
> I also want to redo my disks with dm-crypt+LUKS to keep everything 
secure.
> So basically, I’m looking at RAID + LUKS + LVM...not necessarily in that
> order. (I’ve got a 64gb SSD as the OS drive, so there’s no need to take
> that into consideration. We’re strictly talking about a storage array
> here.) 
> I just can’t make up my mind up on the hard disk configuration. I do 
know
> that I want redundancy and software RAID. I’d  like to mitigate risk, and
> that means not subjecting myself to vendor lock-in from a hardware
> controller just to get a negligible (for my purposes) performance boost.
> 
> But which level of RAID should I use? The horror stories about RAID 5 are
> unnerving; on the other hand, I probably don’t have enough drive slots 
to
> have a RAID 10 array of any appreciable capacity unless I remove the 
2TB
> drive and buy a quartet of 3 or 4 TB drives. How shall I put this.../that’s
> expensive/.
> 
> My server’s mini-ITX motherboard has 6 SATA slots. The SSD takes up 
one,
> which leaves me room for 5 drives. I could probably fit another one in the
> case if I bought a PCI-e SATA controller.
> 
> Any ideas, guys?
> 
> --
> *Justin S. Smith*
> Vice chair/secretary, WPLUG Board of Directors
> http://www.wplug.org[1]
> 
> /"Isn't it ironic that the proprietary software developers call us
> communists? We are the ones who have provided for a free market, 
where
> they allow only monopoly."/
> -Richard Stallman
> 
> --------
> [1] http://www.wplug.org
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