Netgear SC101 SAN
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Before Netgear released their ReadyNAS line of unified storage products, Netgear made a non-Prosafe consumer SAN device called the Netgear SC101 and followed it with the Netgear SC101T. The key difference being that the SC101 used PATA drives and the SC101T used SATA drives.
Over the years I have talked about this device a lot and I own one myself that I keep as an example of what a plain SAN is. The SC101 is excellent for a lab or personal education because it strips a system down to the most fundamental components and gives us a pure SAN with literally zero bells and whistles, not a single feature more than is necessary to be a full fledged SAN other than being, in reality, two SAN units in one enclosure. I love this unit because when people have the idea that SANs are expensive, safe, fast, big or something else, you point them to this. This is as "SAN as it gets." This is possibly the most reference example SAN, the prototypical example, ever made.
Some specs: The SC101 is a two drive toaster with passive cooling. The two drives share a single Ethernet connection but each receives its own IP address (DHCP only, believe it or not!!) Unlike most IP-based SANs, this is not iSCSI but the simpler ZSAN protocol made by Zetera. There is no RAID in the enclosure, each drive is fully independent.
Connecting to the unit is done via a simple ZSAN driver which, sadly, had NTFS as a requirement built into the only public implementation meaning that there was no practical way to use the unit as anything but an unshared, single user NTFS volume - basically the world's slowest and most complicated external hard drive. All of the negatives of a USB drive, few of the benefits.
RAID could be done in software, but, of course, only on the desktop to which this was speaking over ZSAN. This meant that the RAID was happening after the SAN connections were independently in place. So RAID 1 meant that every write had to happen twice... over the network. Cutting the write speed in half. And any network blips, including DHCP ones, would cause the RAID system to see a drive dropping and the array would degrade. It was a disaster and no better than using software RAID on a desktop to RAID to USB hard drives together. Reads faired no better as the network bottleneck was there making the ability to read from two drives at once useless.
Netgear even pushed using this over old Wifi technologies adding to latency and reliability issues.
The SC101 is an amazing device for learning about SANs because everything is open, honest and exposed. There is no hiding behind flashy interfaces, big marketing blitz or layers of non-SAN technology designed to make up for the limitations of SAN itself... it is SAN laid bare for all to see. Using an SC101 is so painful and awkward that you can physically sense the issues with it without needing to really even understand it.
Misconceptions about SAN that this unit fully debunks:
- SAN is Expensive. Hardly, this unit retailed for just $99 and handles two drives, not just one. So it goes slightly beyond the minimum necessary to be a SAN.
- SAN Includes RAID. Often it does, but RAID is in no way part of the definition of a SAN. No RAID here.
- SAN is FC or iSCSI. Those are most common, but many other SAN protocols did and do exist like SAS, USB, IEEE1394, Thunderbolt, ZSAN, FCoE, ATAoE, and more.
- SAN is Reliable. This unit was flaky and failed easily. About as far from reliable as things could be.
- SAN is For Sharing. This doesn't require a basic unit like this to show why this isn't true, but this one exacerbated it by making the only drivers on the market force a non-clustered filesystem making sharing effectively impossible even at higher layers in the stack.
- SANs are Fast. This thing was pathetically slow. Not only was it the performance of a single PATA drive (ATA100) but then pumped over the high overhead of FastEthernet (100Mb/s.) And then, both drives shared a single connection, so only 50Mb/s was ever available to a single drive if the other was in use!
- SANs have Features. Not a single feature here. No snapshots, no backups, no monitoring, no capacity reporting, no drive failure alerts, no communications to the OS to freeze applications.... nothing. Not even an API or an interface!
- SANs can Scale. No growth here. Nada.
- SANs Have Hotswap. No hot swap here, without RAID it would make no sense.
- SANs Have Encryption. Not this one.
- SANs Are Secure. Not even IP level security here, anyone on the network has full access. The SAN technology provides a 100% bypass to even the NTFS ACLs that are on the disk!
So the next time that someone tells you that SAN is awesome because it is a magic box full of unicorn farts and rainbows or tries to say that SAN means that it is bigger, faster or more reliable than NAS or says that they have to slum it with something because they think SAN is overkill or expensive; point them to the SC101 and remind them that the term SAN means nothing more than this, quite literally. This is every bit as much of a SAN as an EMC VMAX, a Dell Equalogic or an HPE 3PAR. SAN is an important technology, but the term SAN means nothing more than block storage over a network (and technically only refers to the network itself.) Understanding the SC101 makes it obvious why depending on SAN to be magic protection makes no sense.
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I've often pointed out that the entire "guts" of the SC101 are nothing but a tiny NIC board that has a PATA controller added to it. There is almost zero logic in the system. It's a 100Mb/s Ethernet NIC (single port) with two PATA ports (or maybe only one, now that I think about it) with just enough basic logic to encapsulate ATA calls into the ZSAN protocol and put that raw onto the network (no security) via whatever IP address DHCP assigns. That's it. No CPU, no cache, no RAID logic, no SMART detection, no alert lights, no network settings, nothing.
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Here is the slightly modified SC101T. Different housing and look, same basics. The SATA and GigE upgrades were significant, but left all of the fundamental issues intact.
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I had an SC101 at one point.
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@brianlittlejohn said:
I had an SC101 at one point.
I kept it as it was such a total disaster yet the best piece of teaching equipment that I ever found.
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Why are we calling them just a SAN when they are a NAS on top of the SAN too.. just like the NetApp NAS devices (which I hate).
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@Jason said:
Why are we calling them just a SAN when they are a NAS on top of the SAN too.. just like the NetApp NAS devices (which I hate).
There is no NAS at all. It's pure SAN. Not a unified device, that was the point. This is one of the rare pure SANs in the SOHO / SMB market (along with Buffalo and Drobo products.) No NAS on top of the SAN here.
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Correct me if I am wrong, but @scottalanmiller calls anything that does iSCSI / block level only a SAN....
A NAS is something that does NFS / Samba / etc.
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@dafyre said:
Correct me if I am wrong, but @scottalanmiller calls anything that does iSCSI / block level only a SAN....
A NAS is something that does NFS / Samba / etc.
Almost any NAS can do iSCSI a SAN is simplier than a NAS..
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@dafyre said:
Correct me if I am wrong, but @scottalanmiller calls anything that does iSCSI / block level only a SAN....
A NAS is something that does NFS / Samba / etc.
That's correct. And something Unified Storage if it does both.
Unified Storage: ReadyNAS, Synology, QNAP, Netapp
SAN Only: Drobo B Series, SC101
NAS Only: Exablox -
@Jason said:
Almost any NAS can do iSCSI a SAN is simplier than a NAS..
Exactly, but a few scale outs don't because of the scale out aspect.
