Does NAS performance matter?

[timofej]

I've read all the material on the site. According to the articles the performance of the NAS does not matter much for everyday needs. However, I still have my doubts.

What I have now:
- DNS-323 (old D-link NAS)
- DIR-655 (gigabit router)
- modern Mac computers

What I need:
- store video/photo library
- stream HD video wireless to other computers
- internal backup capability (from disk 1 to disk 2)

According to the articles on this site my todays setup should be enough. The articles says that very little performance is needed to stream video since there are other bottle necks on the way. Unfortunately, I have different experience. :-(

I'm very unhappy with DNS-323. The device is slow, noisy and formats the disks by it's own. :-/

Even when connected by wire (to my fresh iMac) the picture jerks when I try to watch a DVD (.vob files on DNS). The device is busy at least the first 15 minutes after startup. The disks are spinning up like the device does something when I expect it to be idle. I don't even want to start about the wireless performance... The record is 7 MB/s wired and 3 MB/s wireless for large file transfer.

Well, I decided to upgrade to something newer and hopefully faster and more reliable.

My main question is how fast my NAS needs to be? I look at NASes within two major groups: those that have 50-60 MB/s throughput and those that have 90-100 MB/s. The latter are more expensive of course.

Is the first group enough for me or will I be disappointed again? Or may be the third group 20-30 MB/s is enough? May be all my troubles do not originate from throughput at all but rather from bad DNS software (or something else)?

That was a lengthy question. I hope you were not bored to death while reading it.

 

[teknojnky]

if your primary means of network is wireless, then no it does not matter how fast the nas is. Your wireless will be the limitation and no amout of nas speed will help.

Streaming HD overwireless is highly situational.

in general, for wired network, 50-60 is plenty fast for most people.

But if your constantly transferring very large files (Like blu-rays/rips) then the extra speed of the more expensive devices is really nice.

I would not recommend the 20-30 devices, as they are most likely based upon old/obsolete technology. I would suggest you try to stay with devices with x86/atom based cpu if you can afford it, instead some of the old/lower power marvel/sparc devices.

 

[timofej]

Thank you teknojnky for your reply!

802.11n has theoretically 300 Mbps. That means that I should be safe with the devices that have >40 MB/s throughput.

The devices in this category I've looked at are Qnap TS-212 and Synology DS211. The latter is older and more expensive. Both have Marvell CPU.

Thus, my questions:

1. Is there anything to justify the higher price of DS211?
2. Why is Intel CPU to prefer?
3. Are there any better choices?

My other thought is that even if I use my NAS primarily as a storage device now if I had a faster one I would probably use it as a working disk (photo editing or may be even video editing). Thus, I have one more question:

4. How fast must NAS be to be capable to the work above? If I buy NAS 100 MB/s is it as fast as directly connected hard drive? Where is the bottle neck?

Alternatively I can buy an external enclosure and use it as a working disk.

 

[thiggins]

It sounds like you read this article Can Your NAS Do Two Things At Once?

So even Marvell-based NASes with throughput in the 20 MB/s range should stream HD video fine over 100 Mbps Ethernet.

Even 802.11n wireless will limit performance to under 100 Mbps (12.5 MBytes/s) speeds, best case. This should be fine for HD streaming. But wireless throughput is not consistent enough to support flawless HD streaming in most cases unless your player is smart about buffering.

The DNS-323 is an old design. I don't know what is going on with yours, but you should be able to get a single HD stream out of it. It could be you have a drive that is failing and has a high error rate. Or maybe the disks are very fragmented causing a lot of head seeks, which really will kill performance.

The DS211 and TS-212 are very similar and either has more than enough throughput for HD streaming.

Intel Atom based NASes will generally cost more than Marvell-based products due to higher component count in them. More parts = more cost.

NASes have higher overhead due to the network file system they use.

 

[timofej]

Thank you for your reply Tim!

Yes, I've read this article, as well as all other articles on this site concerning NAS.

I don't know what's wrong with my DNS-323. May be it's just too old.

Anyway, I'm planning to replace it and as I understand the TS-212 would be enough for my needs.

What's about my question #4? If I purchase a really fast NAS (100 MB/s) that's wired to my iMac via Gigabit Ehternet would I be able to edit photo/video directly on it? Is it as fast as an USB2 external drive? Is TS-212 enough for this job? Are there any other bottlenecks on the way?

 

[thiggins]

USB 2 provides about 20, maybe 30 MB/s tops. So a Gigabit connected NAS can be faster in some applications, mostly for large file transfers and streaming. Once you start doing a lot of small read/writes, performance drops steeply.

Go look at the NAS Charts for detailed performance

 

[timofej]

When I work with photo/video editing many small read/writes are done rather than large file transfer. What benchmark does reflect this type of operation? How fast is USB 2 regarding small read/writes?

I'd like to compare with USB because I work with external drives connected by USB2 now. It's not great but it works.

I also assumed that the benchmarks for file copy read and write performance are made for no RAID setup. Is this a correct assumption? I will not raid my NAS since I want to back up one drive to another.

 

[thiggins]

Please read How We Test Networked Storage Devices - Revision 4

There are multiple benchmarks available. Use the dropdown to select them.

 

[timofej]

Oh, thanks. That's the only article I didn't read. :-D I just trusted your tests without going into details. I can see now that I've missed some info.

I can see that you test for RAID 0 if nothing else is said. I guess I should look at RAID 1 values.

Do you have any information about how USB2 stands up with different file sizes?

And my (hopefully ) last question does it matter if I use 5400 rpm or 7200 rpm disks? Or do the 5400 disks overperform the all other bottlenecks anyway?

Many thanks for your help!

 

[thiggins]

This is my last answer (promise!)

No info on USB 2.
Drive speed doesn't matter.

 

[teknojnky]

(NAS) gigabit network = more bandwidth than usb, but higher latency than usb

(DAS) usb = lower latency than gigabit network, but less bandwidth

latency is how much time it takes for read/write requests to respond.

usb/firewire are directly attached to a pc, go through the integrated usb/firewire hub and onto the pci/pcie bus much faster/more direct route to the computers CPU and ram.

going over the network adds the latency the network stack, which is magnitudes slower than usb/pcie/cpu/ram stack.

for photo/video editing, a direct attached usb (or firewire) drive will likely seem to perform better than a network attached NAS.

as the file size gets better, the usb bandwidth limitations can hinder the lower latency, making the usb/firewire slower the bigger the files are.

 

[timofej]

Thank you all for the excellent answers!

I guess I know what I should look for now.

Actually I was looking at TS-412 (with the same performance as TS-212) but... and this is a huge but: I've just found out that Qnap does not have versions backup!!!

What's the point of a backup if I cannot come back and retrieve a file that I accidentally overwrote/deleted, if a file crashed when I saved it and I discovered it a week after that?!!! Just copy files from one place to another is almost the same as RAID (that is not a backup as we all know ;-))! I was sure that all the vendors provide Time Machine-like backup (with hard links). All of them have Unix file systems, why not to use hard links??!!

Very well. I've checked Synology and they do have "real" backup. However their 4-bay NAS (DS411+) costs 780$ here in Sweden (vs 420$ for TS-412) - almost double.

I realize that these two NASes play in different divisions but DS411+ is the only Synology 4-bay NAS that is tested here.

I guess I will have to check other internet resources that do NAS tests.

Anyhow, thanks again for your help. I'm much more aware what I need now. :-D

 

[teknojnky]

erm, hardlinks are not backups either.

 

[timofej]

erm, hardlinks are not backups either.

I'm not sure what you mean. What I meant was that a real backup should handle several copies of files in case a file is accidentally overwritten/deleted/corrupted.

This kind of backup is implemented on different platforms (Mac OS X, Linux) using hard links. Sometimes it's called snapshot backup. Since almost all the NASes use Linux I'm very surprised that not all vendors have included this kind of backup in their software.

The script is really simple and includes a couple of lines. As a matter of fact I used such a script myself on my DNS-323, since it didn't have internal backup included in the software.

The backup solution that Qnap provides doesn't differ much from RAID1. The only difference is that the files are copied scheduled and not immediately, i.e. you have some time to regret your action. How long time you have to discover the mistake depends on the schedule. ;-)

Qnap has also implemented something they call Real-time Remote Replication (RTRR), where the changes are reflected immediately. In this case the only difference I can see is that you can "RAID1" to an external drive/server.

I've already ordered a Synology DS-411+ if somebody wonders. :-D They have something they call Time Backup. I hope the NAS is fast enough that I will be able to work directly on the server.

 

[GregN]

I'm confused, QNAP uses EXT3 Journaling, doesn't that mean you can recover previous versions?

 

[timofej]

I'm confused, QNAP uses EXT3 Journaling, doesn't that mean you can recover previous versions?

I'm as confused as you are. When I didn't find anything in their documentation I was so surprised that I felt that I had to ask them directly.

That's what I got:

Regarding Time-Machine-like backup, do you mean you want to restore to any time-stamp image as you like?

I am afraid to say that we do not support this feature.

We only support one back up for one rsync (backup) job.

We can set the rsync job as incremental backup in order to eliminate the bandwidth usage and backup speed but we only have one copy of backup though.

I still couldn't believe, I thought that they may be had misinterpreted my question and I asked again with some examples how I want backup to work:

1. I want to I be able to go to a chosen date and see what I had on my hard drive that day.
2. I want to be able to see multiple versions of changed files.
3. I want to be able to restore a folder as it was when a certain backup was done.

I got another answer:

As I said, we can only support one "version" of backup.

Have no multiple backup like Time machine at present.

Still discussing how to improve the backup solution.

Sorry for the inconvenience and thanks for your inquiry.

I cannot interpret it in other way that they do not have backup I request.

I must also say that they replied very fast and I would recommend at least their support service.

 

[GregN]

I cannot interpret it in other way that they do not have backup I request.

Jeez, it is journaling, but not at the user level.

It is possible to recover a previous version of a file, but in my case at least, it would require performance enhancing drugs - and traversing the journals by inode.

Write-up about how right here

I guess there is Journaling and there is JOURNALING. It does appear that with there are tools for file recovery, PhotoRec and TestDisk that can manipulate journals.

 

[timofej]

Jeez, it is journaling, but not at the user level.

It is possible to recover a previous version of a file, but in my case at least, it would require performance enhancing drugs - and traversing the journals by inode.

Write-up about how right here

I guess there is Journaling and there is JOURNALING. It does appear that with there are tools for file recovery, PhotoRec and TestDisk that can manipulate journals.

I must say that I don't understand much of what you are saying. Probably, my knowledge in the subject is insufficient.

 

[teknojnky]

the only thing that comes close to timemachine backups, other than actually using timemachine, is readynas replicate (an expensive addon for x86 readynas devices, and you require at least 2 devices and 2 addons).

 

[GregN]

Drobo supports journaling at the user level doesn't it?

I know ZFS provides for the capability, just don't know if there are any interfaces/tools commercially available.