[TriLUG] Storage server diy

[David Burton via TriLUG]

How much storage do you need?

I just picked up several used 2TB SATA drives on eBay, for $20 to $25 each
<https://www.ebay.com/sch/56083/i.html?_fsrp=1&Storage%2520Capacity=2TB&_nkw=-caddy+-case+-enclosure+-USB+-PCB+-Board&_from=R40&Interface=eSATA%7CSATA%2520I%7CSATA%2520II%7CSATA%2520III&LH_ItemCondition=1000%7C1500%7C2000%7C2500%7C3000&LH_PrefLoc=1&_blrs=recall_filtering>.
(I actually bought a total of six, from several sellers, but two tested bad
and had to be returned.) I'm in the process of setting up my "new" DIY
server, running doubly-mirrored drives (3 drives, software RAID1) on CentOS
7.

2TB is more storage than I need, but with drives that cheap, why not? (The
old server it's replacing has mirrored 80GB drives, which is a bit tight.)

(2TB seems like a lot to me. I recall *lusting* after a 10 MB hard disk
drive for my Z80
<http://www.bitsavers.org/pdf/jade/Big-Z/Jade%20Big%20Z%20Rev%20C%20Z80%20CPU.pdf>,
but deciding that I just couldn't justify the expense.)

2TB is the maximum size for MBR partitioning (rather than GPT), and the old
iron that I'm running this on has a non-UEFI BIOS and wouldn't be able to
boot from GPT drives. So to go larger I'd need a separate boot drive. I'd
rather just partition off a 1 GB RAID1 boot partition on the same 2TB
drives.

I imagine 2TB doesn't seem like much storage to many of the folks on this
list, but even with "only" 2TB the RAID1 array still took all day and all
night to sync.

Performance is not a major concern for me, but if you're doing mostly
reads, then Linux software RAID1 mirrored drives are very fast, even when
the drives, themselves, are relatively slow. Two drives are about twice as
fast as one. I assume that three drives are even faster than two drives,
though I've not tested that.

I've also not tested including an SSD in the RAID1 array, but I imagine
that would make it faster yet. It might be that mirroring an SSD with an
HDD would get SSD read speeds with the reliability of RAID1. However, I
don't require extreme speed for this DIY server, so I'm using spinning rust
(HDDs), not SSDs.

I *do* desire extreme reliability, hence 3 drives instead of just 2.

My server will run 24/7, but it will be lightly loaded. So I don't
anticipate a problem with using consumer-grade drives. One of the two bad
drives that I returned was actually an "enterprise storage" drive. I
speculate that typical used consumer grade drives were probably more
lightly used than typical used enterprise storage drives, so the consumer
grade drives might actually be a better bet, if you're buying used.

*Note: *mirrored (RAID1 or RAID10) is the *only* use case for which I would
ever recommend buying used hard disk drives. If you go that route, I
suggest that before buying a drive you first communicate with the seller,
and get their assurance that the drive's S.M.A.R.T. status has been
checked, and it shows zero relocated sectors, zero uncorrectable, and zero
"pending" sectors.

Then, after you receive the used drive, hook it up to a computer, and copy
/dev/zero to the whole thing, and then check the S.M.A.R.T. status for
yourself. Occasionally, a drive that's been sitting in a closet for a long
time, or that has endured rough handling in shipment, might initially show
no bad sectors, but if you run it for a few hours the bad sectors start
showing up. If a drive has even *ONE* relocated or unreadable sector, it is
at drastically increased risk of full failure.

Dave



On Fri, Aug 2, 2019 at 4:07 PM Hariharan Gopalan via TriLUG <
trilug at trilug.org> wrote:

> Is there any storage server expert in the group who can help me with this?
>
> Thanks
> Hari
>