Daisy-chain multiple Asustor NAS units?

[jchny]

I'm close to buying an Asustor AS-5110 along with ten 4TB drives, which I intend to use in RAID 6 mode.

My question is whether that Asustor AS-5110 and other Asustor NAS models can be daisy-chained in close proximity and if so, by what cables and interfaces they would be best connected and what RAID functionality that would enable.

Since each AS-5110 has four Gigabit Ethernet ports, can extra ports be used to daisy-chain two or more Asustor NAS machines together? Can two Asustor NAS machines be connected through Ethernet link aggregation such that it would be like this:

Main Router -----single CAT6-----AS-5110 #1======double or triple CAT6=======AS-5110 #2----------single CAT6--------Main Router

In this text diagram, "Main Router" appears twice but I mean the same router, so that each NAS has its own single connection to the same router but the two NAS devices are connected together with one, two, or three gigabit connections. Would that work?

Or is it better to use USB 3.0, eSATA, or iSCSI to daisy-chain these AS-5110 units together?

Second question, can other Asustor NAS units be daisy-chained?

Thanks!

[Elrique64]

You do know that an NAS stands for Network Attached Storage, right? The USB ports on the NAS is designed to be used to connect devices to the NAS. This is one way to add more HDD space to the NAS, when all the drive bays are full. Add an external enclosure with more drives in it.

These aren't drive enclosures that need a USB connection to work... They are networked devices. When one is on the network, it is available to all the devices on that network, PERIOD. So the ideal connections would be more like this...

Main Router -> NAS #1
Main Router -> Nas #2
Main Router -> NAS #3
Etc...

IF and ONLY IF your router supports link aggregation, you can use both Ethernet jacks on each NAS going back to the router. Otherwise, the jack can be empty. (And probably should be, because if potential problems on the network.) If your router supports Ling Aggregation, then the connection would look more like this:

Main Router => NAS #1
Main Router => NAS #2
etc.

This takes 2 ports off your router for every NAS attached, and gives 2GB Ethernet bandwidth to the NAS. The draw back is, it takes TWO ports on the router! Not everyone has access to a 16 or 32 port router. Most people don't have routers that support link aggregation, either... This is actually some pretty sophisticated networking equipment, and not found in the average home or small business class routers.

You might have the router to do the job, but I think if you did have it, you wouldn't have asked the questions you did.

EDIT: And to actually answer your first question, no, that text diagram wouldn't work, or if it did, wouldn't work well.

[jchny]

Elrique64, thanks for your answer.

I don't think my router has link aggregation, but that's not the primary focus of my question.

I already have a small NAS and plenty of network ports, but I'm new to RAID.

What I'm wondering is whether a RAID volume can be extended beyond the enclosure with additional drives or an additional NAS. Newbie question, I know. Maybe it's a bad idea to even try because having too many drives in the RAID array will result in extremely long write times and rebuilding times.

Reading the material on ASUSTOR University made me wonder if there are some limits I don't know about.... Can the Asustor AS-5110 even make a ten-drive RAID 6 volume or is it limited to 8 drives per RAID volume, with perhaps multiple RAID volumes within the enclosure.
Is there a TB limit, in that enclosure, for the size of a single RAID 6 array?

I have seen the term "daisy chain" used by other NAS enclosure makers, but I don't understand 1) exactly how daisy chaining would work, 2) whether Asustor has the daisy chaining feature at all.

Maybe, as you suggest, the best way to get more RAID capacity is simply to add more RAID volumes on additional NAS enclosures on the same network rather that try to daisy chain them directly to each other to make one gigantic RAID volume.

Your thoughts?

[Elrique64]

Elrique64, thanks for your answer.

I don't think my router has link aggregation, but that's not the primary focus of my question.

I already have a small NAS and plenty of network ports, but I'm new to RAID.

Actually the "daisy chaining" question you brought up with your text diagram is the main focus of Link Aggregation. What you had won't work very well, if at all, and has nothing to do with Raid configurations.

What I'm wondering is whether a RAID volume can be extended beyond the enclosure with additional drives or an additional NAS. Newbie question, I know. Maybe it's a bad idea to even try because having too many drives in the RAID array will result in extremely long write times and rebuilding times.

No, Raid arrays can't be extended past the physical device itself. Let's look at this for a minute....

Let's say I have a 4 bay NAS, and a 2 bay external enclosure connected to it via USB or eSATA. Let's say that I can make an array across all 6 drives (just for the sake of the discussion.) I make a 6 drive Raid 5 (or 6) array. Now, for some reason the enclosure that was attached via the USB or eSATA cable somehow loses connection to the NAS. All of the data on the NAS is potentially GONE until that external drive gets reattached. In the BEST situation, the array is in a degraded state, so I can still get to it, but any loss of a drive in the NAS itself and it's all gone. The benefits of having the drives in the array are pretty much lost, because of the external device not being connected.

This gets even more complicated trying to have an array spanning Ethernet connections. Any congestion on the network and the array breaks. I'm sure there are ways to do this out there, but I wouldn't want to put MY data at risk this way.

Reading the material on ASUSTOR University made me wonder if there are some limits I don't know about.... Can the Asustor AS-5110 even make a ten-drive RAID 6 volume or is it limited to 8 drives per RAID volume, with perhaps multiple RAID volumes within the enclosure. Is there a TB limit, in that enclosure, for the size of a single RAID 6 array?

There is a size limitation to a single drive array, and I think I read someplace that the limits for the 20x and 30x series of NAS's was like 12TB or somewhere in that neighborhood. For the 50xx, 60x and 70xx series I think it's as high as 24 or 36TB, but I could be wrong. Going off of old memory here...

I have seen the term "daisy chain" used by other NAS enclosure makers, but I don't understand 1) exactly how daisy chaining would work, 2) whether Asustor has the daisy chaining feature at all.

Maybe, as you suggest, the best way to get more RAID capacity is simply to add more RAID volumes on additional NAS enclosures on the same network rather that try to daisy chain them directly to each other to make one gigantic RAID volume.

Your thoughts?

Synology uses the term "Daisy chaining" when they talk about some of their external enclosures attaching to their NAS's through some sort of proprietary connection. (It could be through USB or eSATA, too, I don't really know...) This just adds a larger pool to the over-all storage capacity. I don't think they actually have those drives as part of a Raid housed in both boxes. (see above) Remember, too... You aren't sharing the DRIVE to the clients, you are sharing a share point. that share point might BE the top level of the drive, but it also might not be, depending on how you have things set up.

When you start building Raid Arrays, one of the first things you have to look at is "How many drives can the array lose before the array is broken." Having 10 drives in the array isn't a bad thing, unless losing two drives breaks it completely. That's 10 potential points of failure in a system. As one drive has failed already, the other 9 now have a bit more wear and tear going on. There is potential for another failure from the increased activity. Rebuilding the array could also hasten a drive's failure, as you are doing more thrashing on the drives to recreate the array...

Now, mind you I'm not saying you WILL have a failure. I'm saying the chances of a failure of a second drive increases after losing one and you are either running degraded or rebuilding the array.

Building a Raid system you also have to look at how large of a storage system you might need. If 10TB is enough for you, 4 or 5 drives in Raid 5 might be the ticket (Raid 5 is basically losing one drive of capacity, so 5 x 4TB drives, raid 5 = roughly 16TB. 4 x4TB is roughly 12TB) Believe it or not, that is A LOT OF STORAGE! I have over 1300 movies on 2 x 3TB drives now, (roughly 3.5TB out of 6TB total.) and over 10,000 TV episodes on a raid 5, 5x3TB enclosure... (10TB total space on the enclosure after the raid. I'm using about 4.4TB now, with 10K episodes and 30K high res photos.)

If you really need THAT much storage space, you are doing a lot more with the equipment than I am, and I think I'm doing a lot.... I'm not suggesting you don't NEED that much storage capacity. We are talking BOAT LOADS here, though.... And if you are needing that much storage then a 5110 might be too small for your needs. It's a smaller processor than the 7010. The 7010 might be a better fit over-all for your use case. You have to decide that yourself.

[jchny]

Elrique64,

Thanks for your further answers...it's starting to gel.

My application is a large set of 8mm and 16m film transfer archives that the lab tells me will amount to about 12TB but could be more.

My goal is to put them on a RAID 6 array and also to leave room for me to archive some of my other files of a few TB.

I won't need high performance, just long-term reliabilty and the ability to link the archive to Dropbox or Google Drive for a second backup.

The AS-5110 with some number of 4TB drives looks more than adequate; I am thinking maybe I should make two RAID 6 volumes of 5 disks or one 6 disk volume for the film archive and a second 4 disk volume for my other stuff.

I was thinking it would be more efficient to make one single RAID 6 volume with all 10 drives but maybe the 5110 can't make a single 40TB (32 TB usable under RAID 6) volume with ten drives...so I might just have to sacrifice some efficiency (10 drives on RAID 6 being 80% efficient with space, 5 drives being only 60% efficient) if the 5110 has a limitation.

I'm going to post the drive limit question in a separate thread...I did not see drive limits anywhere in the documentation.