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NAS solutions for the paranoid - question

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Dr. Slack

Sat Jul 26 2008, 11:55AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

I feel I need some form of network accessible large reliable attached storage, but am paranoid about hardware failure and long term compatibility / reliability. I have 3 XP and one *ptt* Vista *ptt* machine, on a router box at present, with haphazard sharing of printers and discs.

As far as I can see, it is fairly easy to get a 2 HD NAS box configured as raid 1, with a print server thrown in, for not too much money. This should do all I want it to do while it is working. My concern over this solution is the nature of the drive formatting and use, so that if the box breaks I - best case - am forced to buy that particular brand of replacement box or - worst case - they've gone out of business so I not be able to get my data back off the discs. Or does the fact that most boxes I've seen that state a disc format as ext2 or ext3 are therefore obviously *nux based, so any *nux box will do?

My alternative is to think about a single HD NAS with a USB HD plugged in (or an empty box with 2 external), which although slightly more expensive, sounds much more flexible to me. It might be that the box s/w can raid 1 the internal and external drives (do they need to be identical size, or track/cylinder config, or manufacturer for this?), though I've not spotted claims for this anywhere. If not, then it should be fairly straightforward to arrange backup s/w to image the internal drive onto the external one. The point about this arrangement is that the USB drive can be plugged into anything in the event of NAS failure, and replaced by any USB drive if it fails.

What do you use or recommend, am I being a wuss?

Steve Conner

Sat Jul 26 2008, 12:35PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

My philosophy is to keep a duplicate copy of everything that's valuable. So I have a NAS (it's actually an old Compaq PC running Linux) that mirrors the hard drives on my other machines. The NAS itself is not RAIDed, but if its hard drive ever blows, I can rebuild it from my other computers using the rsync scripts on them. Likewise if any of my other computers go, the data on them is on the NAS.

Of course, the main loophole here is if my house goes on fire, or someone breaks in and steals all of the computers. I think that's an acceptable risk for much of my own personal data, but for paid work, I use an off-site backup. So my computer at work is backed up on a removable HD that I keep hidden at home, and vice versa.

This may seem paranoid, but I've worked with computers for years and had a few hard drives crash on me. With this system, I've always been up and running again within a day or two, and I've never lost more than a day or two's worth of work. (Touch wood!)

Oh, and watch out for those Netgear NAS that use a proprietary format.

aonomus

Sat Jul 26 2008, 01:24PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

I use freenas, works on most spare computers and supports tons of backup protocols.

...

Sat Jul 26 2008, 04:42PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

I would strongly recommend using a solution based on mdadm under linux, because then if the controller/enclosure/etc explodes you can plug the drives into any box with a livecd and you data comes back instantly (as long as you have the 'persistant superblock' turned on), where as if you are using a hardware raid or 'fakeraid' propriotary software raid when your controller dies you need to replace the controller with an identical one or your data is gone.

Depending on how many drives you need, you can get a SATA card (note, the sil3124 works well, the cheaper 3114 are utter crap, don't use the internal or 'driver' provided with either of them just use the normal linux kernel module and mdadm) and plug the drives into that, and it might be cheaper (and its certinly faster) than getting usb enclosures for the drives. Of course then you also need your spare computer to have a sata card, but most recent mobos have them onboard now.

Carbon_Rod

Mon Jul 28 2008, 03:15AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

For the paranoid:

NetBSD running software based RAID 0+5
Encrypted fs
kerberos
IPsec VPN configuration

rsync redundancy OS mirror on 10Gbs fiber-optic connected secondary system(s).

Cheers,

Tiberius

Mon Jul 28 2008, 03:15AM

Registered Member #1484 Joined: Wed May 14 2008, 03:24PM
Location: Cary, NC, USA
Posts: 27

My NAS setup right now consists of a i386 Gentoo Linux host with a PCI-X Sil3124 as mentioned above using a slightly hacked driver for port multiplier support (probably not necessary with newer kernels). The Sil3124 controller I'm using has a single external Infiniband connector allowing me to run 4x SATA channels to an external enclosure. This enclosure is a 9x 5.25" bay CD duplicator case which currently has one port multiplier and one 5 3.5" in 3 5.25" hot swap enclosure and room for 2 more. The port multiplier(s) are attached at one end to a fan-out PCI bracket which has an external Infiniband port and 4 internal SATA ports. Currently I am using 1M eSATA-to-SATA cables as the only port multipliers available at the time I originally specced this out offered eSATA connections. I have been experiencing a slightly elevated CRC error rate resulting in occassional port resets, but no data integrity issues so far. There are now port multipliers which offer internal SATA connection for the drive and controller connections, allowing one to eliminate all but 6"-8" of internal cabling, I am pretty sure this would reduce error rate to an insigificant level.

This configuration does add around US$ 250 interface cost per 5 drives including port multiplier, Infiniband cabling, and Sil3124 controller, but it really has been quite stable for me:

thunder ~ # uptime
23:05:15 up 158 days, 9:01, 8 users, load average: 1.07, 0.92, 0.75
thunder ~ # df -h
Filesystem Size Used Avail Use% Mounted on
...
/dev/evms/md/md3 1.2T 1.1T 21G 99% /export/archive

Local performance exceeds gigabit speeds even with only a single SATA channel utilized, I am pretty sure with all 4 channels utilized it would be limited by the PCI-X bus:

thunder ~ # time dd if=/dev/evms/md/md3 of=/dev/null bs=$((128*1024))
7023+0 records in
7022+0 records out
920387584 bytes (920 MB) copied, 6.36346 s, 145 MB/s

real 0m6.395s
user 0m0.012s
sys 0m4.900s

I would say similar results can be achieved on the cheap with the same software stack, a Sil3124 with eSATA connections, and an eSATA port multiplier enclosure. eSATA offers exactly the right combination of performance and flexibility for personal external storage while USB is utter crap in comparison.

Steve Conner

Mon Jul 28 2008, 11:05AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

On the other hand, that's only about a factor of 5 faster than a USB 2.0 external drive that you can buy in a store, and use without a degree in hardcore geek studies. For redundancy, just buy two and rotate them.

I wouldn't want a setup like that unless I did a lot of video editing, or 24-track pro audio or whatever. It'll make a lot of noise and eat a lot of power.

Tiberius

Mon Jul 28 2008, 11:14PM

Registered Member #1484 Joined: Wed May 14 2008, 03:24PM
Location: Cary, NC, USA
Posts: 27

I certainly agree that most can live without terabyte-sized volumes on their LAN, I was just trying to illustrate the remarkable capabilities of SATA. In simple configurations comparable to a single drive USB setup, feature set is similar, performance is greater, and cost should be similar or even lower.

Indeed for single drives up to 2-4 drives you can skip pretty much all of what I described. At that point you just need single drive eSATA enclosures and an eSATA controller -- much like the USB configuration. They even make PCI brackets to convert internal SATA ports to eSATA ports saving you on the cost of an eSATA controller if that's the avenue you want to take. I believe eSATA enclosures are priced comparably to USB enclosures if not cheaper as the USB enclosure will include active SATA and USB controllers while the eSATA enclosure can be passive aside from the power supply. However, unlike the USB approach which already significantly bottlenecks in even a single drive configuration, you can expand an entry-level SATA storage system to offer greater performance, availability and capacity with much less cost overhead than any "traditional" enterprise or prosumer storage system.

Regarding the performance -- that volume is a poor example as it is being bottlenecked by a timing issue between the port multiplier and the Sil3124. eSATA generally imposes no overhead whatsoever, it's simply an external cable spec and wider signal tolerances for the existing SATA standard. To illustrate, linear throughput of a single drive in the previously benchmarked array (still through the port multiplier, but not being bottlenecked by it at this throughput):

thunder dev # dd if=/dev/sde1 of=/dev/null bs=$((128*1024))
3650+0 records in
3649+0 records out
478281728 bytes (478 MB) copied, 7.59381 s, 63.0 MB/s

storagereview.com finds for the same model disk a maximum transfer rate of 66.5MB/sec.

Incidentally, I just did a quick search and found a single-drive eSATA enclosure for 15.99$ and a two-channel PCI Express Sil3132 eSATA controller for 24.99$. The Sil3132 has even better performance than the Sil3124, achieving around 250MB/sec per host channel with the same port multipliers I use, though realistically that is irrelevant for a single drive configuration.

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