Best NAS RAID Mode level?

Deleted member 952 · Mar 5, 2022

Hi,

My Synology DS218J NAS 16TB Network Attached Storage, I'm not sure which RAID mode to use before I was using RAID 1 but apparently defragging isn't allowed. So I'm looking at switching to Synology Hybrid RAID (SHR), is this same as RAID 1 where it mirrors 2 drives. As I'm using 2x8TB drives where they mirror each other so I don't lose any data.

Which would you guys recommend I use which would let me use File System Defragmentation (BTRFS file system)

Thanks for any help

Berton · Mar 5, 2022

As to the RAID level, I just yesterday received a NAS unit with 2 x 2TB drives to replace my current NAS setup, am now debating with myself if I want RAID 0 with its striping of both drives or RAID 1 with mirroring one drive to the other. As I understand it, each has a downside, striping gives 4TB capacity but if one drive fails all data is lost while mirroring allows recovery if one drive fails but total capacity is only 2TB. My main use of a NAS drive is for storage of data and downloaded programs for access for any computer on my network.

cereberus · Mar 6, 2022

Businesses use Raid system because drives are often multi user and store critical business data. They would never use Raid 0.

The decision in domestic use depends on what you are using drive for. If data is critical, then Raid 0 is not a good idea.

However Raid 1 reduces your capacity by 50%.

If you do not use Raid but just have two separate drives, a pragmatic approach is that you could partition each wirh say 1 TB for critical data, and 1 TB for non critical data.

You then mirror the critical data on both drives but not non critical data. That way, your effective capacity is 3 TB.

If course, this approach requires a bit of user management.

If capacity is not an issue, and you are sure you want Raid, then Raid 1 is safer than Raid 0.

The decision as to what you do depends on data, criticality, and capacity needs. Only you can assess that.

jimbo45 · Mar 6, 2022

RAID 0 on Linux / QNAP type RAID systems if you do it by software (package MDADM) is perfectly OK as you can then have devices of different sizes and use the entire capacity of your HDD's. It works essentially as "JBOD" Just a bunch of disks but much faster as I/O is paralleled across all the devices whereas in "JBOD" mode disks get filled up sequentially.

However disadvantage is that with RAID 0 - if you lose any disk within the array you lose the lot. My experience is though that decent HDD's are robust and reliable and breakdowns are actually quite rare these days. The speed improvement in RAID 0 plus the convenience of being able to "Mix HDD sizes" to get the maximum storage IMO is worth it. -- Make sure though you back up data in case you need to re-build the array.

There's no correct answer here -- obviouslly if you are runing "critical missions" you can't afford an outage so RAID 0 wouldn't be of any use but for typical home LAN's using NAS systems then RAID 0 can make decent sense -- but you Must take backups regularly.

(I've had RAID 0 running for around 3 years now mainly 24/7 on two NAS systems -- I've only needed to replace 1 HDD because of failure and around 6 HDD's due to "hardware" upgrades for bigger, faster drives. I've 100% confidence in my systems and the backup stategies in place).

NAS 1 2 RAID 0 Arrays array 1 -- 2 X 4TB HDD's, array 2--- 2 X 5 TB HDD's

NAS 2 1 RAID array array 1 --4X 6TB HDD's.

Disk failure these days really is comparatively rare and the speed of RAID 0 is IMO well worth it -- even using software RAID the speed improvement is massive. Just ensure you have a decent backup strategy in place.

For Linux type NAS systems rsync and its GUI version GRSYNC is excellent for managing backups and can easily be run regularly via crontab process.

Incidentally some external HDD enclosures often have a built in selectable RAID system too so those can be worth looking at as well if you have some spare HDD's / older HDD's that you could use.

Cheers
jimbo

cereberus · Mar 6, 2022

jimbo45 said:
RAID 0 on Linux / QNAP type RAID systems if you do it by software (package MDADM) is perfectly OK as you can then have devices of different sizes and use the entire capacity of your HDD's. It works essentially as "JBOD" Just a bunch of disks but much faster as I/O is paralleled across all the devices whereas in "JBOD" mode disks get filled up sequentially.

However disadvantage is that with RAID 0 - if you lose any disk within the array you lose the lot. My experience is though that decent HDD's are robust and reliable and breakdowns are actually quite rare these days. The speed improvement in RAID 0 plus the convenience of being able to "Mix HDD sizes" to get the maximum storage IMO is worth it. -- Make sure though you back up data in case you need to re-build the array.

There's no correct answer here -- obviouslly if you are runing "critical missions" you can't afford an outage so RAID 0 wouldn't be of any use but for typical home LAN's using NAS systems then RAID 0 can make decent sense -- but you Must take backups regularly.

(I've had RAID 0 running for around 3 years now mainly 24/7 on two NAS systems -- I've only needed to replace 1 HDD because of failure and around 6 HDD's due to "hardware" upgrades for bigger, faster drives. I've 100% confidence in my systems and the backup stategies in place).

NAS 1 2 RAID 0 Arrays array 1 -- 2 X 4TB HDD's, array 2--- 2 X 5 TB HDD's

NAS 2 1 RAID array array 1 --4X 6TB HDD's.

Disk failure these days really is comparatively rare and the speed of RAID 0 is IMO well worth it -- even using software RAID the speed improvement is massive. Just ensure you have a decent backup strategy in place.

For Linux type NAS systems rsync and its GUI version GRSYNC is excellent for managing backups and can easily be run regularly via crontab process.

Incidentally some external HDD enclosures often have a built in selectable RAID system too so those can be worth looking at as well if you have some spare HDD's / older HDD's that you could use.

Cheers
jimbo

All good advice but in the end if capacity is not an issue, Raid 1 is safer as data is inherently backed up.

For most users, speed is not really a major issue.

Can you have say a 1 TB drive and a 2 TB drive, and set up a 1 TB partition mirroring 1 TB drive in Raid 1 mode, and then use remaining 1 TB for noncritical data?

jimbo45 · Mar 6, 2022

cereberus said:
All good advice but in the end if capacity is not an issue, Raid 1 is safer as data is inherently backed up.

For most users, speed is not really a major issue.

Can you have say a 1 TB drive and a 2 TB drive, and set up a 1 TB partition mirroring 1 TB drive in Raid 1 mode, and then use remaining 1 TB for noncritical data?

RAID 1 -- I think the problem is here that for mirrored drives they need to be the same size so you would get 1 TB mirrored and the other 1 TB -- ???? probably unuseable especially if the HDD's are attached to a hardware RAID card -- would depend on the hardware as Windows has no real "Native" software RAID system.

Windows can create mirrored volumes though -- you need two vols (min) of course and need to set them up as dynamic disks and then with disk management you can create a mirrored volume. That should give you a 1TB mirrored "partition" with the other 1 TB useable as not part of the mirrored partition. I've got no idea though how recovery would work for that HDD though.

I still think even with "Classical RAID 1" you need to backup data anyway -- IMO you can't have too many backups and cheap external 4 and even 5 TB self powered USB "passport" type drives IMO are brilliant for that purpose e.g backup music / video etc.

Cheers
jimbo

cereberus · Mar 6, 2022

jimbo45 said:
RAID 1 -- I think the problem is here that for mirrored drives they need to be the same size so you would get 1 TB mirrored and the other 1 TB -- ???? probably unuseable especially if the HDD's are attached to a hardware RAID card -- would depend on the hardware as Windows has no real "Native" software RAID system.

Windows can create mirrored volumes though -- you need two vols (min) of course and need to set them up as dynamic disks and then with disk management you can create a mirrored volume. That should give you a 1TB mirrored "partition" with the other 1 TB useable as not part of the mirrored partition. I've got no idea though how recovery would work for that HDD though.

I still think even with "Classical RAID 1" you need to backup data anyway -- IMO you can't have too many backups and cheap external 4 and even 5 TB self powered USB "passport" type drives IMO are brilliant for that purpose e.g backup music / video etc.

Cheers
jimbo

I was more curious than a desire to do this - for most users, I suspect RAID is just not really needed, and a simpler NAS server with two drives is adequate, and you use software to sync critical data.

Deleted member 952 · Mar 6, 2022

Is Synology Hybrid RAID (SHR) same as RAID 1? My data is critical I cannot lose it, I was using RAID 1 before but it says it's not compatible with File System Defragmentation.

Berton · Mar 6, 2022

Just a guess, anything happening in RAID 1 has to happen on both drives at the same time, can interfere with some drive features.

pparks1 · Mar 7, 2022

As a systems engineer for a living, these are my thoughts.

RAID 1 is primarily for OS drives and such and it's really protecting immediately your ability to boot a critical system in case a hard drive fails. It never suffices as a "backup" because if you get a virus, malware, or inadvertently delete a file, you lose the duplicate side immediately. You should always have a regular backup in place to protect your data.

RAID 0 is great especially when testing or when you need the fastest IO you can get. Again, if any drive in that array fails, you lose it all. You should always have a regular backup in place to protect your data.

Other RAID levels like Raid 5, Raid 6, Raid 10 or Raid 50 are used in business environments for preservation of data in the case that drives fail. These provide the best balance of speed and performance along with space capacity potential. The level you use is determined by a number of things, primarily the application that you are running on the server. For example, with a SQL server with a high data write rate, a RAID level of 10 is often preferable to RAID 5 as you aren't having to calculate parity on all of those rights. And business class systems typically use enterprise class RAID controllers which provide much higher levels of performance than software raid.

jimbo45 · Mar 8, 2022

Hi there

@pparks1

One thing you omitted in your reply is certainly of relevance to many HOME users :

Another advantage of RAID 0 particularly if you have systems that have a good software RAID system such as mdadm then you can mix devices having unequal sizes and the whole data area is available -- e.g a 1 TB HDD and a 1.5TB HDD can be configured as a RAID 0 array of 2.5 TB and also will balance I/O across both devices - so even if the Disk speeds are different then speed is "optimised" for both devices.

But if you lose a Disk then the whole array goes so you need to back up data regularly (which you should be doing in any case).

For home users who have spare HDD's with unequal capacity or older HDD's lying around RAID 0 makes decent sense for gaining extra capacity - without having to split large files or libraries such as Music Data bases / Video files over several HDD's.

BUT HAVE BACKUP.

My experience though is these days decent HDD's rarely if ever fail these days even when used 24/7 --but again "ad Nauseam" they CAN fail so have backup.

Cheers
jimbo

pparks1 · Mar 8, 2022

@jimbo45

As far as failures go, I think those of us who live in the enterprise world are a bit skewed in our opinions on failure rates. On enterprise SAN's and NAS devices, they are very proactive towards fail and they scan the drives and they predict when they believe that a failure may occur. So we replace drives at a much higher frequency rate that typical home users might.

But generally speaking, I do believe they are pretty reliable.

mavin · Mar 8, 2022

RAID 10 all the way

pparks1 · Mar 8, 2022

mavin said:
RAID 10 all the way

Raid 10 is great for speed and the ability to lose up to 50% of your drives. However, it's terrible for storage lost, as you only get 50% of your raw capacity.

Dru2 · Mar 10, 2022

mavin said:
RAID 10 all the way

pparks1 said:
Raid 10 is great for speed and the ability to lose up to 50% of your drives. However, it's terrible for storage lost, as you only get 50% of your raw capacity.

RAID 10 user here on a Western Digital NAS box holding 4 WD Red Pro drives. The advantage is speed and redundancy, this disadvantage as pointed out by pparks is loss of half your storage. Out of a possible 24TB, I only have 10.7TB available.

Anyway, I'm just using 3TB of the 10 available, so...

_Tachyon_ · Mar 10, 2022

snapraid can be a good alternative to RAID if all you're looking for is backup protection for DATA drives... I use it on my data server.

SnapRAID

A backup program for disk arrays. It stores parity information of your data and it recovers from up to six disk failures

www.snapraid.it

jimbo45 · Mar 11, 2022

Even on a NAS you should still backup its data regularly -- you don't have to back the entire thing up daily but either do differential / incremental or backup specific directories at regular intervals.

For home users if you do (and you should) backup NAS regularly there's absolutely no reason why you shouldn't use RAID 0 -- fast and uses entire capacity of drives.

How many home users with a NAS are running "Mission critical" applications where the NAS needs to be online 24/7. The MTBF ("Mean time before Failure") of even domestic HDD's is very good these days so rebuilding arrays should be a very rare occurrence.

With a NAS - frequent switching on and off is the most likely cause of disk problems - decent HDD's consume very little power when idling - start up and slow down causes most wear on bearings, fans, and other mechanical parts. Leave the NAS on 24/7 if possible.

Cheers
jimbo

Ghot · Mar 11, 2022

kuyenmotdivad said:
Hi,

My Synology DS218J NAS 16TB Network Attached Storage, I'm not sure which RAID mode to use before I was using RAID 1 but apparently defragging isn't allowed. So I'm looking at switching to Synology Hybrid RAID (SHR), is this same as RAID 1 where it mirrors 2 drives. As I'm using 2x8TB drives where they mirror each other so I don't lose any data.

Which would you guys recommend I use which would let me use File System Defragmentation (BTRFS file system)

Thanks for any help

You could just use Karen's Replicator.

Karen's Replicator the Backup Utility for Windows v3.7.6 Released May 25, 2020 | Karen's Power Tools | Karen's Software

Automatically backup files, directories, even entire drives! Karen's Replicator copies selected files from one drive/folder to another. Source and Destination folders can reside anywhere on your network.

www.karenware.com

You can schedule it to "copy" what's on one drive (part or all), to the other.
It only copies what has changed since the last time it ran.
This way, you get the advantages of mirrored, BUT, defrag still works.
Best of all... there's no RAID to deal with.

I'm sure there are other programs that can do this. But I've been using Replicator since the XP days.
Never had even one problem.

jimbo45 · Mar 11, 2022

_Tachyon_ said:
snapraid can be a good alternative to RAID if all you're looking for is backup protection for DATA drives... I use it on my data server.

SnapRAID

A backup program for disk arrays. It stores parity information of your data and it recovers from up to six disk failures

www.snapraid.it

Hi folks
I think whatever RAID system (or none) you use on NAS servers you STILL need to back it up regularly. The Mirroring system can protect against one drive failing but what if the MOBO itself fails or the OS gets a glitch or a user accidentally or maliciously deletes data.

Seems many here regard RAID 1 as sufficient for 100% of data protection and never worry about backup.

False "economy". Even the most experienced of people have accidentally deleted data at times. Some data from corrupt disks can't be recovered no matter what the "Spiel is" on the backup / recovery program. What happens also if the server gets destroyed via lightning strike, accidental damage -- fluids (cofee / beer etc split into it), electrical cable failure (rodents etc eating bits of cable), cpu / mobo failure, machine is "stolen" etc etc.

Some or most of these are unlikely to happen but people have experienced all these things so if you have important data that can't be re-created elsewhere you need to back it up away from the NAS regularly -- imagine having to re-rip 3,000 CD's again --even if you still had the CD's and that assumes they were still readable too. Some of those self powered 4 or 5 TB external USB drives are ideal for NAS backups.

Cheers
jimbo

Brizzle · Mar 12, 2022

@kuyenmotdivad

I have a DS220j with 2 x 2TB HDDs configured as Synology SHR which I use to store photographs - I'm a professional photographer so they are critical files to me. SHR acts as a mirror so I only get 2TB of storage but can tolerate one drive failing just like RAID 1. The difference is that SHR allows you to replace a failed drive with another of different capacity, which is useful if you later decide you need bigger drives as they can be changed one at a time with the NAS mirroring from old to new each time.

Whilst I don't want to decry the comments by others above, suggesting/discussing the merits of RAID 5 or RAID 10 is irrelevant to the OP as he has a two bay NAS. No offence meant to anyone :)

What I do agree about though is that a NAS is not a complete backup solution and you need to have at least two other copies of your critical files elsewhere, one of which should be off-site.