Increase storage with RAID 0?

Nick0 · 18. Februar 2020

Hello all,

I have two OMV setups, one using a 1TB drive for storage with all of my data on it which is accessible through FTP and network drives on MAC computers. All that suff is sent via r-sync for backup, to a second OMV installation with 2X 500GB drives (only one is needed for data storage at present since the 1TB drive on the other OMV install is under half used).

I would like to utilise the full storage on the second OMV install, and one idea I had was to create a RAID 0 array to make use of both of the 500GB disks.

My limited understanding is that I would need to wipe both 500GB first, therefore losing my backups and the I suppose I would need to make adjustments to FTP and r-sync services on both OMV installs in order that they refernce the correct drives.

Am i missing anything here, or is there maybe an altogether easier way to span all of the data from the 1TB disk over the 2 500GB ones?

Thanks you,
Nick.

ryecoaaron · 18. Februar 2020

If you just want to pool the drives for more storage, look at the unionfilesystems plugin.

Nick0 · 18. Februar 2020

Thanks! not dabbled with plugins yet, so its about time I did!

All the best,
Nick.

cabrio_leo · 18. Februar 2020

Zitat von Nick0

one idea I had was to create a RAID 0 array

If you use a RAID 0 you will loose the complete data of both disks if one of them fails. RAID 0 was / is used to increase performance.

Nick0 · 18. Februar 2020

Hi there,

Yes, i understand that. The RAID 0 disks would be holding the second copy of all the data, so if one of them failed I would still have a back up on the initial data copy held on the primary installation of OMV.

All the best,
Nick.

Nick0 · 18. Februar 2020

OK, so I have installed the plugin and merged the two drives. Can anybody tell me if I need to alter FTP or r-sync settings now?

Thanks,
Nick.

ryecoaaron · 18. Februar 2020

Zitat von Nick0

Can anybody tell me if I need to alter FTP or r-sync settings now?

They both should use the pool now. You could change the shared folder to use the pool instead a single drive.

Nick0 · 18. Februar 2020

OK, thanks,

I have edited the shared folder path for just one folder and it looks like it has updated in FTP and the r-sync module but when I run the job, I get this:

Please wait, syncing </srv/dev-disk-by-label-storage01/jack/> to <ftpuser@192.168.1.99::jack> ...

sending incremental file listrsync: failed to set times on "." (in jack): Operation not permitted (1)./

sent 201 bytes received 92 bytes 586.00 bytes/sectotal size is 56,235,809 speedup is 191,931.09rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1196) [sender=3.1.2]

The synchronisation has completed successfully.Done ...

Thanks,
Nick.

ryecoaaron · 19. Februar 2020

Is the OMV system with the pool the sender or receiver? From that output, the error is on the receiver side.

HannesJo · 20. Februar 2020

Zitat von cabrio_leo

If you use a RAID 0 you will loose the complete data of both disks if one of them fails. RAID 0 was / is used to increase performance.

I dont think so. Since everyone here knows(?) that a RAID is no backup but can affect the availability of data in case of disk failure, one may say RAID0 could affect uptime of your services or so. But no data is lost. It just needs to be restored from a backup. Otherwise someone could think that his data is safe while not using RAID0. May be a better tip to say USE A BACKUP IN ANY CASE.

Nick0 · 20. Februar 2020

Zitat von ryecoaaron

Is the OMV system with the pool the sender or receiver? From that output, the error is on the receiver side.

Yep, that's the receiver side. I disabled it for troubleshooting because I had another problem but I will put it back later, I hope. Sorry for the late reply - do you know if there is any documentation for the plugin as I have a few questions.

Thanks,
Nick.

ryecoaaron · 20. Februar 2020

Zitat von Nick0

do you know if there is any documentation for the plugin as I have a few questions.

Documentation? Not sure. I just write/maintain the plugins and not good at writing documentation that noobs could use. So, I just don't write any. Video? probably. There is lots of documentation for mergerfs though - https://github.com/trapexit/mergerfs/blob/master/README.md

crashtest · 20. Februar 2020

Zitat von HannesJo

I dont think so. Since everyone here knows(?) that a RAID is no backup but can affect the availability of data in case of disk failure, one may say RAID0 could affect uptime of your services or so. But no data is lost. It just needs to be restored from a backup. Otherwise someone could think that his data is safe while not using RAID0. May be a better tip to say USE A BACKUP IN ANY CASE.

There are two separate issues here:
- First, backup is not just a good idea, it's required if a user/admin wants to insure their data is not lost.
- Second, if one disk is lost when using RAID0, all data on both disks is lost. With the network (1Gbs) as the bottle neck, where RAID0's increase I/O can't be utilized, RAID0 has no practical application in a home NAS. It merely increases the chances of a data disaster.

Good backup allows users to take risks in testing new approaches or techniques, but there should be something of value in it. For a home NAS application, RAID0 has no practical benefit. For combining the storage of two disks, the UnionFS plugin is safer and more beneficial.

HannesJo · 20. Februar 2020

Zitat von crashtest

There are two separate issues here:- First, backup is not just a good idea, it's required if a user/admin wants to insure their data is not lost.
- Second, if one disk is lost when using RAID0, all data on both disks is lost. With the network (1Gbs) as the bottle neck, where RAID0's increase I/O can't be utilized, RAID0 has no practical application in a home NAS. It merely increases the chances of a data disaster.

Good backup allows users to take risks in testing new approaches or techniques, but there should be something of value in it. For a home NAS application, RAID0 has no practical benefit. For combining the storage of two disks, the UnionFS plugin is safer and more beneficial.

Yes I know and I mostly agree. Nevertheless, I think these warnings like "Dont use RAID0, you are going to lose your data" cause many people thinking "Oh ok, then I dont do that and my data is save". No word about backups. Thats why there are lots of people asking how to restore lost data that was not protected by backups but by fancy raid setups. What do U think is the reason for all the people thinking "Oh I need RAID5" or so, but have never spent a minute thinking about backup?
In my eyes, it must be communicated more often that the most important thing about data safety is a backup. What RAID is used is more a question of data availability. That's why I question it when someone says with RAID0 your data is in danger. No With RAID0, your uptime is in danger. Your data is only in danger if there is no backup of it, no matter which RAID U use.

Nick0 · 20. Februar 2020

Zitat von ryecoaaron

Documentation? Not sure. I just write/maintain the plugins and not good at writing documentation that noobs could use. So, I just don't write any. Video? probably. There is lots of documentation for mergerfs though - https://github.com/trapexit/mergerfs/blob/master/README.md

OK, yes - I get that this isn't rocket science but I thought I might learn a bit more about how it actually works. Thanks for your time in providing us with these tools.

Cheers,
Nick.

Nick0 · 20. Februar 2020

Zitat von HannesJo

Yes I know and I mostly agree. Nevertheless, I think these warnings like "Dont use RAID0, you are going to lose your data" cause many people thinking "Oh ok, then I dont do that and my data is save". No word about backups. Thats why there are lots of people asking how to restore lost data that was not protected by backups but by fancy raid setups. What do U think is the reason for all the people thinking "Oh I need RAID5" or so, but have never spent a minute thinking about backup?
In my eyes, it must be communicated more often that the most important thing about data safety is a backup. What RAID is used is more a question of data availability. That's why I question it when someone says with RAID0 your data is in danger. No With RAID0, your uptime is in danger. Your data is only in danger if there is no backup of it, no matter which RAID U use.

I am not sure who tou're trying to convince here. Everybody in this thread seems to agree with you regarding the importance of backing up data.

ryecoaaron · 20. Februar 2020

Zitat von Nick0

I get that this isn't rocket science but I thought I might learn a bit more about how it actually works.

I can answer questions you have but writing up everything I know about the plugin is not going to happen

HannesJo · 20. Februar 2020

Zitat von Nick0

I am not sure who tou're trying to convince here. Everybody in this thread seems to agree with you regarding the importance of backing up data.

lol. Totally missed my point.

Nick0 · 20. Februar 2020

Zitat von HannesJo

lol. Totally missed my point.

Oh, apologies - I thought your point was that people need to be more aware of the importance of backing up, instead of thinking that RAID is a one-stop fix for that and a whole lot more. Everybody seems to be of that same opinion, so that's what made me wonder. Not being awkward or anything, I honestly thought that was what you were getting at, and I would agree 100% with you, but apparently, you meant something else.

Nick0 · 20. Februar 2020

Zitat von ryecoaaron

I can answer questions you have but writing up everything I know about the plugin is not going to happen

OK, that's kind of you and thanks.

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