ext4 or btrfs on Synology

[neufuse Veteran]

The latest DSM version defaults to formatting volumns with BTRFS, while I know there are advantages to this file system, do you really gain anything over just going with ext4? It from what I've read seems like a relatively new file system. I'm not really a linux person so I don't have the largest knowledge on the two file systems.

 

Is it better to just stick with ext4 for now? it seems like btrfs uses more disk space up since it versions (i assume ext4 doesn't from the light reading i've done on the two?)

[Blue-Vision]

Btrfs has issues and isn't to be depended on for long-term storage, whereas ext4 was made for it. Since you've pretty much answered your own question by the statement "btrfs uses more disk space", yeah. Ext4 is the clear choice of the two.  

[neufuse Veteran]

  On 11/09/2016 at 23:31, Unobscured Vision said:

Btrfs has issues and isn't to be depended on for long-term storage, whereas ext4 was made for it. Since you've pretty much answered your own question by the statement "btrfs uses more disk space", yeah. Ext4 is the clear choice of the two.  

Expand  

Well all I knew about BTRFS was the journaling part and that take, and that synology pushes it as the default file format now.... I put a new volumn on and it went right to btrfs... probably should redo that as Ext4, which is what I've been using for the other volumns

[+BudMan MVC]

"Btrfs has issues and isn't to be depended on for long-term storage"

 

Where did  you read this??  Why would it not be good for long term storage???

 

To be honest for a storage system btrfs would be hands down the most logical choice period!! 

[Mindovermaster Global Moderator]

  On 12/09/2016 at 19:43, BudMan said:

"Btrfs has issues and isn't to be depended on for long-term storage"

 

Where did  you read this??  Why would it not be good for long term storage???

 

To be honest for a storage system btrfs would be hands down the most logical choice period!! 

Expand  

I found that fishy as well. For desktop use, yes, EXT4 is better. But for server/storage with several disks, BTRFS is better all around.

[Blue-Vision]

  On 12/09/2016 at 19:43, BudMan said:

"Btrfs has issues and isn't to be depended on for long-term storage"

 

Where did  you read this??  Why would it not be good for long term storage???

 

To be honest for a storage system btrfs would be hands down the most logical choice period!! 

Expand  

Too many reports of btrfs flaking out and destroying the data stored within the file system. The guy that does the Linux Action Show had a run-in with it about a year ago, iirc, and was quite vocal about how badly it treated him after a mere weekend of use.

 

[EDIT] Here's the whole incident. 

 

https://www.youtube.com/watch?v=WfpNGJt40Lc&t=3384s (The point where he finally loses his cool about btrfs)

Edited September 13, 2016 by Unobscured Vision

[+BudMan MVC]

So 1 idiot on youtube??  without even 5k views?  Over a year ago..  So that was posted Apr 2015, so that was what version at best 3.19.1?  Maybe 4?

 

https://btrfs.wiki.kernel.org/index.php/Changelog

 

So we are now version 4.7.2, think maybe a few improvements?

 

So synology has now made it their default??  Do you think that would be a wise choice for a company that makes nas's for their bread and butter if their was even a slight chance it could flake out and wipe all their users data??  Does that sound plausible??  Mindovermatter was their red flashing lights, bells going off warning warning warning you could loose data using this??

[IceBreakerG]

I'm using btrfs on my DS1815+. I have 3x6TB WD Red drives in it, and it's set up for 1 drive parity. I haven't had any issues with the file system at all. Pretty much every issue I've had so far has been with DSM 6.0, but they've since been cleared up (mainly issues with packages not running). It's been running solid for about 3 months or so now.

[Radium]

BTRFS is fine if you stick with the non-RAID and RAID 0 or 1 setups. RAID 5 or 6 is NOT safe. I've used BTRFS for close to 2 years now and I haven't experienced any data loss or corruption. I make use of RAID 1 with LZO compression and snapshots. I've experienced power outages and system freezes caused by others things than the file system. I've never lost data.

[Mindovermaster Global Moderator]

  On 13/09/2016 at 02:24, BudMan said:

So 1 idiot on youtube??  without even 5k views?  Over a year ago..  So that was posted Apr 2015, so that was what version at best 3.19.1?  Maybe 4?

 

https://btrfs.wiki.kernel.org/index.php/Changelog

 

So we are now version 4.7.2, think maybe a few improvements?

 

So synology has now made it their default??  Do you think that would be a wise choice for a company that makes nas's for their bread and butter if their was even a slight chance it could flake out and wipe all their users data??  Does that sound plausible??  Mindovermatter was their red flashing lights, bells going off warning warning warning you could loose data using this??

Expand  

[neufuse Veteran]

  On 14/09/2016 at 00:30, Radium said:

BTRFS is fine if you stick with the non-RAID and RAID 0 or 1 setups. RAID 5 or 6 is NOT safe. I've used BTRFS for close to 2 years now and I haven't experienced any data loss or corruption. I make use of RAID 1 with LZO compression and snapshots. I've experienced power outages and system freezes caused by others things than the file system. I've never lost data.

Expand  

Synology for RAID5 and RAID6 default to BTRFS in DSM6

 

One thing I'm noticing is it uses up a lot more CPU time doing file level stuff, the check disk (raid error checking) / defrag take a lot longer to run, and of course uses up a good bit more space keeping change logs for files

[Jason S. Global Moderator]

  On 14/09/2016 at 02:35, neufuse said:

Synology for RAID5 and RAID6 default to BTRFS in DSM6

Expand  

what do you mean by this? i dont understand

[neufuse Veteran]

  On 14/09/2016 at 20:19, Jason S. said:

what do you mean by this? i dont understand

Expand  

when you make a RAID5 or RAID6 volume it defaults the format to BTRFS as part of the creation, you have to explicitly tell it now no use ext4, which was previously the only format they used

 

I only brought that up because of the previous poster saying don't use it on RAID5 and RAID6 because it's not safe... if it wasn't safe I don't think they'd make it the default format

[+BudMan MVC]

"if it wasn't safe I don't think they'd make it the default format"

 

There you go using logic again   Didn't you watch the youtube video put out by that guy.. Clearly btrfs is a complete ###### show and your going to loose your data.  Which is why Synology has switched too it I am sure, they clearly want all their users to have a crap experience with their products..  And loose their data, maybe they got a dmca about their users storing copyrighted material and this is their way of getting rid of it heheheh ROFL

 

Or maybe they just didn't see that video and don't understand that is not safe, and went ahead and enabled it and made it default without any testing of it at all.. Yeah that's prob it

[Radium]

  On 15/09/2016 at 01:06, neufuse said:

when you make a RAID5 or RAID6 volume it defaults the format to BTRFS as part of the creation, you have to explicitly tell it now no use ext4, which was previously the only format they used

 

I only brought that up because of the previous poster saying don't use it on RAID5 and RAID6 because it's not safe... if it wasn't safe I don't think they'd make it the default format

Expand  

BTRFS has RAID 0, 1, 5 and 6 built in. That's what I'm talking about. Synology most likely uses MD-RAID 5 or 6 and then put BTRFS on top of it. That's completely different.

 

BTRFS RAID is configured during or after you set up the filesystem (using btrfs-progs).

If you create a RAID and pick a filesystem after the RAID has been configured then it's either hardware RAID or MD-RAID.

People have reported unrecoverable data loss from RAID56 in BTRFS. It even warns you on the BTRFS Wiki about it.

Based on this, Synology most likely uses MD-RAID, especially when you can(?) pick your own filesystem for the RAID. BTRFS is perfectly fine when run on top of a block level RAID since it doesn't do RAID itself when you do that.

[Jason S. Global Moderator]

MD-RAID? oh god, yet another acronym to learn.

[+BudMan MVC]

You mean the wiki article that states

 

any system which might encounter unplanned shutdowns (power failure, kernel lock-up), and it should not be considered production-ready.

 

I completely agree that unplanned power failures or just plain lockup of the OS (kernel) could cause you loss... How is this not an issue for any raid system anywhere?  This is one of the reasons raid cards have battery backups.

 

So you have your synology just plugged into wall power?  Or do you have it using a UPS, and then planned shutdown before loss of battery power on power loss?

 

 

[neufuse Veteran]

  On 15/09/2016 at 14:48, BudMan said:

You mean the wiki article that states

 

any system which might encounter unplanned shutdowns (power failure, kernel lock-up), and it should not be considered production-ready.

 

I completely agree that unplanned power failures or just plain lockup of the OS (kernel) could cause you loss... How is this not an issue for any raid system anywhere?  This is one of the reasons raid cards have battery backups.

 

So you have your synology just plugged into wall power?  Or do you have it using a UPS, and then planned shutdown before loss of battery power on power loss?

 

 

Expand  

Oh I always plan ahead my unplanned outages

[+BudMan MVC]

Agreed as we all should..

[neufuse Veteran]

  On 15/09/2016 at 11:42, Radium said:

BTRFS has RAID 0, 1, 5 and 6 built in. That's what I'm talking about. Synology most likely uses MD-RAID 5 or 6 and then put BTRFS on top of it. That's completely different.

 

BTRFS RAID is configured during or after you set up the filesystem (using btrfs-progs).

If you create a RAID and pick a filesystem after the RAID has been configured then it's either hardware RAID or MD-RAID.

People have reported unrecoverable data loss from RAID56 in BTRFS. It even warns you on the BTRFS Wiki about it.

Based on this, Synology most likely uses MD-RAID, especially when you can(?) pick your own filesystem for the RAID. BTRFS is perfectly fine when run on top of a block level RAID since it doesn't do RAID itself when you do that.

Expand  

MD-RAID? Area you talking about "Multiple Device RAID"? Gawd I had to look this up... so BTRFS does it's own version of software RAID to span across multiple disks or volumes or it could be BTRFS as standalone file system split over a hardware RAID array (which is what sinology is doing)? am I getting this right?

[Radium]

  On 15/09/2016 at 20:39, neufuse said:

MD-RAID? Area you talking about "Multiple Device RAID"? Gawd I had to look this up... so BTRFS does it's own version of software RAID to span across multiple disks or volumes or it could be BTRFS as standalone file system split over a hardware RAID array (which is what sinology is doing)? am I getting this right?

Expand  

You've got it right. There are benefits to do it like BTRFS and ZFS compared to relying on hardware RAID or an intermediate software RAID layer. You lose performance but RAID is more about reliability and uptime than performance. Having the filesystem in on it allows you to have an odd number of drives and mismatched drives when you mirror your data. It also allows you to add and remove drives on the fly while the filesystem is online, just to mention some features.

[Zakman12]

Reviving an old thread because I found it (so others will as well) while investigating the use of Btrfs on striped RAID arrays on Synology.  Here is their response:

https://www.synology.com/en-us/knowledgebase/DSM/tutorial/General/What_was_the_RAID_implementation_for_Btrfs_File_System_on_SynologyNAS

 

"However, it is known that Btrfs RAID is unstable and not suitable for production environments. For this reason, Synology chose Linux RAID over Btrfs RAID. The following diagram explains the concept - Synology has implemented the layers in between to ensure that we have full control of the communication for the highest stability."

[camaxide]

Does this mean it’s now safe to use btrfs in a raid 6, or not? I run raid 6 to ensure my files are as safe as they can within one file system, so it’s important it has a minimal chance to fail

[Blue-Vision]

No. Use ext3/4 (Linux raid). Far more stable. That's what Synology was saying. Btrfs RAID isn't supported at all due to data corruption issues.

[dyn]

  On 12/12/2017 at 00:45, Unobscured Vision said:

No. Use ext3/4 (Linux raid). Far more stable. That's what Synology was saying. Btrfs RAID isn't supported at all due to data corruption issues.

Expand  

That isn't what they are saying at all. Synology isn't using the RAID functionality of BTRFS since it has issues and isn't production ready (as the official BTRFS wiki is telling the rest of the world). It is this RAID functionality that people mean when they are saying that RADI5/6 with BTRFS gives issues (read: data corruption).

 

What Synology is doing, is what just about the entire storage world has been doing for years: they layer. You start with hardware RAID (which requires a RAID card) or software RAID (which can be something that is part of the OS such as MD) and on top of that you put the filesystem (ext4, BTRFS, ZFS, NTFS, APFS, HFS+, etc.). There are also other options where you can put more layers. That's exactly what the picture given by @Zakman12 shows: Synology uses software RAID and puts BTRFS or ext4 on top of that.

 

In this case you can opt for MD (or Linux RAID as Synology calls it) or Synology's own software RAID which they call Synology Hybrid RAID (SHR). Next you pick what filesystem should be used: ext4 or BTRFS. This means that you can pick whatever RAID level you want without it wreaking havoc on the BTRFS filesystem that you put on top of it.

 

So once more:

• RAID functionality in BTRFS = trouble
• separate RAIDed volume with BTRFS on top like Synology does it = no issues
• To stress: Synology is NOT using the RAID functionality of BTRFS at all

Thus: the way Synology does it makes it safe to use RAID6 and BTRFS. 

 

However, the use of RAID6 is debatable. Most are using RAID10 instead. If you want to know more about that I suggest to search around by starting with the Wikipedia article on RAID.

 

Btw, by no means is ext3/ext4 Linux RAID. They are filesystems and do not have any form of RAID functionality. You need a newer generation filesystem such as BTRFS or ZFS for that. When using ext4 you therefore need something else to do the RAID part. That, the issues with BTRFS' RAID functionality and their desire to control the RAID part is probably why they are using MD and SHR.

Edited December 31, 2017 by dyn