[CALUG] Recommendations for NAS with Solid State Drives

Bryan Smith me at bjsmith.me
Mon Aug 2 23:27:17 EDT 2021

On Mon, Aug 2, 2021 at 10:33 PM Thomas Delrue <thomas at epistulae.net> wrote:

> Does anyone have experience and/or recommendations for a good NAS with
> Solid State drives? Has anyone done this or am I crazy for even wanting
> to do this?

Almost all NAS (and SAN) solutions over the last five-plus (5+) years are
either two (2) types ...
 - Hybrid NAND cache and optional buffer + platter-backed (i.e., platter is
the permanent store), and ...
 - NAND-only (no platter)

This is definitely so as NAND not only overtook 2.5" in density, but can
far fit more in 2.5" than 3.5" platter can.
E.g., Samsung PM1643 can fit 30TB in 2.5" x 15mm, and 10-20TB in 7-10mm
high, and still use no more than 12W (12V at 1A), and often under 5W.

There are variants on the Hybrid NAND solution, especially since NAND
cells *'wear
out' *on writes much faster than magnetic platter, and have a much higher
error rate (although such is compensated by firmware).
But pure NAND NAS/SAN are now becoming very common.

E.g., I just spec'd out an IBM SVC 2.5" shelf with 0.7PB (0.5PB) usable in
a 2U chassis.
It's only a matter of cost (30TB is about $5K).

Are there folks running a QNAP device with a properly RAIDed solid state
> drive-based array? What are the things to keep in mind, do or
> specifically not do?

Before that, consider the fact that there are several types of NAND
interfaces.  I'll start with the one you know.

AHCI/SATA - This is the legacy SATA physical connection, legacy host
controller interface -- compatible going back to the old IBM PC/Seagate
ST506 commanding

SATA, in the 3rd iteration (aka SATA3), as you already know, is ~6Gbps
(~0.6GBps at typical 10:8 encoding).
There is also SAS (Serial Attached SCSI-3), which in quad-channel (SAS uses
more conservative signaling), is ~12GBps (~1.2GBpsat typical 10:8
encoding), aka SAS 12Gbps.

AHCI/PCIe - This is the new PCIe x1-4 channel physical connection, but
still with the legacy interface for full OS/legacy boot compatibility
nVME/PCIe - This is the new PCIe x1-4 channel physical connection, and with
the new, far more parallel interface, but it is not legacy compatible
(e.g., need new firmware/OS for boot)

PCIe 3.0 in a single x1 lane is capable of 10Gbps (~1GBps at typical 10:8
encoding), which is another 2/3rds as fast as SATA in throughput, so x2 is
over 3x faster, x4 is over 6x faster.
nVME can also command far more efficiently, and to far more I/O operations
than legacy ST506 compatible AHCI that is traditionally used.

When it comes to actual, physical interfaces, there are several now that
exist beyond SATA.

M.2 slot (22mm/0.9" wide, 20-80mm/0.8-3.2" long) - Depending on the keying
type, whether B, M or other, there are SATA and/or PCIe x2 or x4 lanes
U.2 connector (cable) - This is the 'cabled' variant of M.2, actually based
on 'SATA Express' (SATA/SAS-connector based, but SATA + PCIe x2), but only
provides PCIe x4 lanes (no SATA)

So ...

What you're looking for is to find a NAS that can maximize the benefits of
NAND devices, especially with M.2 nVME/PCIe x4 (or U.2 nVM/PCIe x4 when it
comes to lots of drives/bays).
I assume this is just for a SOHO system with maybe 5-6 drives max in
RAID-6, to give the equivalent 'usable' 3-4 capacity.

E.g., (6) 1TB drives in RAID-6 = 4TB usable (equivalent of 4 drives usable)

Now that assumes pure NAND.
If you're looking for hybrid, there are various options ... including NAS
devices that can provide 1-2 M.2 nVME/PCIe x4 slots.
There are others than only have 2.5" bays.

E.g., I have a tiny little (2.5" based) Synology DS620 (no nVME/PCIe, only
AHCI/SATA) and I've populated it as follows ...
(4) 5TB 2.5"x15mm SATA platters in RAID-5 for 15TB usable
(2) 0.5TB 2.5"x7mm SATA NAND for cache+buffer (read+write) in RAID-1 (write

Synology requires two (2) NAND devices for buffer (write), otherwise just
using one (1) NAND device, will only enable cache (read-only).
E.g., I could have done ...
(5) 5TB 2.5"x15mm SATA platters in RAID-5 for 20TB usable
(1) 0.5TB 2.5"x7mm SATA NAND for cache-only (read-only)

- In terms of how to access the data: NFS is the only real requirement,
> no samba, or whatever. But scp would be nice too...
> Like I said: I'm fine sticking with QNAP. I just don't know if I'm crazy
> for wanting to stuff it with solid state drives (would NVMe be doable?)
> instead of spinning rust ones...or whether this is doable at all.
> Are there other considerations that I should take into account?

The biggest problem I have with most SOHO NAS devices is they suck for NFS,
and aren't really NFSv4 feature complete.  I use them more for iSCSI block
(as well as as a media server) but that's another story.

> Are there other vendors that I should look at that specifically offer a
> device like this?

I'd be interested in finding a capable SOHO NAS vendor that offered IPA +
NFSv4 out-of-the-box so I can *'drop in'* a low-power ARMv8 or BGA
(embedded) x86-64 with POSIX (UNIX/Linux) Identity + File in one system.
But most vendors are targeting the 98% of SOHO customers that run Windows.

- bjs

Bryan J Smith  -  http://www.linkedin.com/in/bjsmith
E-mail:  b.j.smith at ieee.org  or  me at bjsmith.me
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