NAS versus Standard hard drive. - Page 1
Forum section: electronics / general

author: donnyDA
author_rank: Newbie
timestamp: December 23, 2022, 04:34:08 am
content: Would like some input for this one,A statement was made that NAS drives do not support sector reallocation. From what I'm given to understand in the statement, the writer believes that sector reallocation is carried out by the raid controller card. Therefore he concludes that NAS should not be used as regular desktop drives.I always thought that NAS were just repurposed regular drives with additional mechanical robustness.The other statement was that NAS uses lower power, but when you look at the ratings, a NAS actually has a higher current draw on both rails.So it leads me to suspect the first statement even more.

author: BradC
author_rank: Super Contributor
timestamp: December 23, 2022, 05:17:12 am
content: Yeah, a lot of tripe."NAS" drives are just artificial segmentation of the market. The real difference that makes them more suitable in a RAID is the ability to limit read retries (WD call it TLER) and it is implemented using the SCT/ERC command set.A standard desktop drive that doesn't implement that can go off into the weeds for minutes while trying to read a dud sector. If that time exceeds the timeout on the RAID controller (or stack above it) then the controller will try and get the data from elsewhere, then write it back to the drive with the duff sector.Because that drive is still off in the weeds, it ignores the write command and that causes the RAID controller to deem it dead and eject it from the array. By limiting the recovery time (don't try too hard because if you can't read it I can get it elsewhere and write it back to you) it makes the whole process much more reliable (and faster).Other than that, there's not much in it. I have a set of old WD Green drives that were the last before they switched off the SCT/ERC commands in the "consumer" level disks. Prior to that, most drives were usable in a RAID configuration.Same goes for "Surveillance drives". All the tripe about being unsuitable for daily use because they are allowed to return duff data in the name of expedience, preferencing writes over reads and more marketing gumph. They *can* do those things, if you use the ATA Streaming command set, but nobody really does and your OS and RAID controller certainly won't. The only difference I've noticed in extensive testing between the WD Purple and Red drives is the Purple are cheaper, and they have their power saving hardwired off (so no head parks, and no spin down). I automatically switch those off on RAID configurations anyway, so they work out cheaper to use.So the big one is if you intend on using drives in any form of redundant scenario, make sure they support SCT/ERC.

author: David Hess
author_rank: Super Contributor
timestamp: December 23, 2022, 01:55:57 pm
content: Quote from: BradC on December 23, 2022, 05:17:12 amThat is the major difference. Many desktop drives supported TLER in one form or another until manufacturers, or at least Western Digital, noticed people using them in RAID applications and removed that feature. Western Digital Black desktop drives supported TLER up to and including the 750GB models. After that, Western Digital removed TLER from their Black line.There are other claimed differences like resistance to vibration which can cause head tracking errors.NAS drives definitely support sector reallocation. I know that if a bad sector is written to, the drive will reallocate it if the sector is bad, and that is exactly how a RAID controller handles it. I have watched it happen and the standard procedure to clean a drive of bad sectors is to write to every one.

author: niconiconi
author_rank: Frequent Contributor
timestamp: December 23, 2022, 04:30:54 pm
content: Quote from: donnyDA on December 23, 2022, 04:34:08 amThis sounds like nonsense to me. I refuse to believe it unless I see a citation from a reliable source.If it's true, software RAID would never work. Solaris & FreeBSD's ZFS has a pure software RAID implementation called RAID-Z, and it has been successfully used in many serious production environments. As far as I know, ZFS doesn't have any special low-level code to manually reallocate sectors on the HDD.QuoteAnd different level of warranty. Customer-grade HDDs are often not warrantied for 7x24 operations. Vendors may refuse your warranty claim if they knew you're using it on a server. But "video surveillance", NAS and Enterprise-grade drives are warrantied for this.There can be firmware differences, as other posters have mentioned.

author: vad
author_rank: Frequent Contributor
timestamp: December 24, 2022, 09:35:08 pm
content: Quote from: donnyDA on December 23, 2022, 04:34:08 amIf that statement was true then NAS drives should not be used in … NAS. Majority of NAS devices do not have RAID controllers, and implement software RAID. Quote from QNAP: “ Our RAID is software RAID, and hardware RAID is not supported. Our software RAID uses the Marvell SATA controller and Intel CPU to give our NAS devices fast performance levels.”PS. In 2023 people should not use NAS drives in desktops. For local storage, NVMe SSD is what you should be after. For everything else - consider NAS and Cloud.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 25, 2022, 12:25:53 am
content: Quote from: vad on December 24, 2022, 09:35:08 pmA modern HDD like the Exos X18 is rated for 270MBps. That would require at least 5G Ethernet to not get bottlenecked, which only a small minority of users have.I don't see very many disadvantages to having a HDD in addition to a SSD. Root filesystem goes on the SSD, HDD is used for bulk storage.

author: David Hess
author_rank: Super Contributor
timestamp: December 25, 2022, 02:42:43 pm
content: Quote from: vad on December 24, 2022, 09:35:08 pmNAS drives are still useful for bulk storage in desktops which would be uneconomical with SSDs. The workstation, which is made largely from desktop parts, that I built last year has 8 x 3TB with a hardware RAID controller, although in retrospect I wish I had used fewer larger disks. The local bulk storage is faster than similar report storage without the networking hassle.Quote from: NiHaoMike on December 25, 2022, 12:25:53 amThe sequential transfer speed is not something which can normally be relied on, although a RAID array does better and I regularly saturate 2Gb/s ethernet connections.QuoteI may end up reconfiguring my workstation like that, but I want to add redundancy to the boot SSD. Currently I boot from a volume on the RAID but this lacks some flexibility.

author: BradC
author_rank: Super Contributor
timestamp: December 26, 2022, 01:44:09 am
content: Quote from: David Hess on December 25, 2022, 02:42:43 pmI put a pair of cheap 120GB SATA SSDs in for EFI and boot partitions in RAID1.root and home are on a separate (encrypted) RAID comprised of a 1TB NVMe in RAID1 with a RAID0 of 4 SATA SSDs. That gives me the native read performance and latency of the NVMe, and the writes are still approaching 2GB/s. Not ideal, but it's quick and the best I could do given I/O limitations in the machine.

author: Halcyon
author_rank: Unknown
timestamp: December 29, 2022, 02:46:44 am
content: So-called "NAS" drives, is mostly marketing wank aimed at the consumer market. You really need to consider the application (hardware RAID vs software RAID), size of the system and the specifications of the drive.NAS drives typically (but not always) have a error recovery control enabled (also known as TLER or CCTL depending on the manufacturer), or it's switchable through software. This basically limits the time taken for error recovery. With this enabled, if the drive encounters a read/write error, it will give up after a shorter period and report the failure back to the HBA/RAID controller to deal with. Typically, this timeout is shorter than the timeout of the RAID controller. In drives with no ERC limit set, it may try continually (and for long periods) to recover from the error, which presents as a unresponsive/failed disk to the RAID controller, which in effect will cause it to drop out of the array.Manufacturers often claim that NAS drives are more reliable and are designed for 24/7 operation, however in all my years in the industry, I haven't come across a disk yet that isn't "designed" for all day, everyday operation. You may want to consult the MTBF or TBW specification for the drive(s) you're looking at, to give you some idea.Some drives (even ones labeled suitable for NAS) use shingled magnetic recording (SMR). This was/is particularly true for some of the WD Red/Blue/Black and Seagate Barracuda and Skyhawk drives. Whilst these might not present much of an issue or a performance hit in smaller NAS systems, but as arrays grow, they can be a real bottleneck, particularly with some of the drive-managed SMR (DM-SMR) drives like the WD Red's. (As far as I'm aware, the Seagate IronWolf series uses CMR/PMR exclusively).I stopped using consumer-grade drives about 15-20 years ago, even for my home NAS setup. They were just too much of a headache. However, these days, traditional hardware RAID is basically considered "old-school" in favour of better, and more resilient software-based setups (like ZFS), so consumer drives may be less of an issue (and more tolerated), but do your research and plan your system properly.Even though significantly more expensive, I only buy enterprise grade drives (like the WD/Hitachi Ultrastar's). Even second-hand, they've proven to be a very reliable drive for many years. I had an array of 2TB drives running continuously for over 10 years and are still good today (although I retired them for larger drives).As I always say when it comes to IT/Technology:There is no one-size-fits-all solution.You generally get what you pay for.If something appears "cheap" there is usually reason for it, which might not be favourable for you.There is more than one right way to do things.Consider what's most important to you: Cost vs. Performance, vs. Reliability; Pick two.

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: December 29, 2022, 10:37:38 am
content: I'll always use a NAS drive simply for the TLER and not having any warranty issues in the case where power-on hours exceeds 8 hours per day (the limit for desktop drives). I'm also using some second hand SAS drives and they've been great so far.But ultimately there are only 2 kinds of hard drives. Those that have failed and those that haven't failedyet. RAID(Z) is not a backup, practice 3-2-1 backup strategy. Power surge or a lightning strike can toast your whole machine so have an offline, offsite copy of anything irreplaceable.

author: Jeroen3
author_rank: Super Contributor
timestamp: December 29, 2022, 12:06:58 pm
content: Is anyone actually still using hardware raid??You know, with the (very expensive) dedicated raid cards with their own little sodimm and battery?

author: BradC
author_rank: Super Contributor
timestamp: December 29, 2022, 01:22:52 pm
content: Quote from: Jeroen3 on December 29, 2022, 12:06:58 pmAbsolutely. Every larger CCTV NVR or NAS that gets installed has a hardware RAID card. Anywhere from about 6-24 bays. Even Dell and Supermicro storage boxes use them by default.

author: Halcyon
author_rank: Unknown
timestamp: December 29, 2022, 11:47:55 pm
content: Quote from: Jeroen3 on December 29, 2022, 12:06:58 pmEhh it depends. It's almost considered "legacy" nowadays with far better alternatives. Last lot of Dell servers we bought, it was still an option but not the default. (Or they came with them in just normal HBA mode and you had to buy the RAID add-on, BBUs etc...).A lot of people are still comfortable with hardware RAID despite its drawbacks and I think that largely comes from the adage of "it's always better to do it in hardware", particularly how much software RAIDs (particularly those consumer ones which weren't "proper" RAIDs) sucked back in the day. Microsoft didn't help with their Dynamic Disks either (I ran into more problems than solutions with that).These days, I think it's the opposite. Whilst hardware RAID controllers still have uses, those uses are no where near as popular as they used to be. I'll use ZFS again as one good example of software "RAID" that is far superior to the hardware-based stuff you get, I can't think of a single thing a RAID card does better.Happy for anyone to challenge me on these points.(Also, I'm going to move this thread over to Computing.)

author: BradC
author_rank: Super Contributor
timestamp: December 30, 2022, 02:37:33 am
content: Quote from: Halcyon on December 29, 2022, 11:47:55 pmAllow the use of Windows as the OS with any form of parity raid when you want actual storage performance.Yes I know Server 2019 finally learned how to do double parity in "Storage Spaces", but its performance is like a three legged dog with gout, and that's before we get into recovery scenarios.They still have their place in many elements of "the enterprise". Those of us lucky enough to use non-windows OS have had frighteningly good, solid performing software RAID solutions for decades, but Windows is still playing catch up and for those scenarios popping an expensive HBA into the box solves all those issues quickly.

author: David Hess
author_rank: Super Contributor
timestamp: December 30, 2022, 07:33:20 pm
content: Quote from: Jeroen3 on December 29, 2022, 12:06:58 pmIf you know what to look for and can accept older hardware, then it becomes relatively inexpensive. The advantage for me is that it allows my Windows boot volume to be part of the RAID.