Time Taken to Migrate Raid5 Array to Raid6

[Chopmeister]

I currently have my media stored on as ASUSTOR NAS (AS608T, which has an Intel Dual Core Atom processor clocked at 2.13Ghz, and 1 GB of Ram).

It's populated by 5 6TB drives in a RAID5 array (showing 12TB used, 10TB free). I have decided that to mitigate against risks of disk failures I will migrate the volume from RAID5 to RAID6. And yes, I know RAID does not constitute a backup, at the moment all the files are duplicated on USB drives and I'm also working on a better backup plan.

I have already placed the 6th drive in the NAS to use as the second parity drive.

I'm not a big fan of leaving stuff running while I'm not home, and have heard stuff like:

• it could take 50 hours to complete the migration; and
• it has to be done in one run, if the NAS is powered off during the migration then it won't work.

Expanding the RAID5 volume did let the NAS be powered down part way through, and on re-starting it just picked up where it left off.

Does anyone know how long a RAID6 migration is likely to take on this sort of hardware, and whether it really can't be powered down part way through and resumed later?

[SameSelf]

And yes, I know RAID does not constitute a backup

+++++1 for knowing this. Most do not and perpetuate the myth that it is.

As for migrating, ahhhhh, one of the many problems with RAID that few contemplate until the time arrives. This is when tape drives come in very handy. Honestly, RAID is getting really long in the tooth. If I were you with that much data, I would take a serious look at more modern file systems like openZFS (it's Ubuntu's default). RAID was never really designed for such large spans.

[raffriff42]

Your rebuild will fail not only if you have a power failure, but also if you get an unrecoverable read error at any time during the process -- possibly on some data you haven't accessed in years, and thus have no idea that it is bad. I've heard stories, sad ones...

https://en.wikipedia.org/wiki/RAID#Weaknesses

Better to do a full backup and build a new RAID from scratch, rather than attempt to rebuild in place. Best not to do it at all.

I don't think going from one to two parity bits is worth the effort - or the decrease in write performance. Personally I wouldn't relay on parity at all - I would do RAID 0 plus frequent (coffee break) backup to a JBOD plus daily backup to something else, such as "the cloud" or a portable drive that goes off site.

By "backup", I don't mean backing up to proprietary file format - I mean simply copying the files that are new or changed. There are free programs that make this easy. One I am using now (but is not perfect, occasionally fails to read files located deep within Windows user folders, but is fine for normal data) is called Create Synchronicity.

[ron spencer]

If you have all the files already "duplicated on USB drives", just use those as your source files and blow away your RAID and start over. This is easier, safer, and yes, faster.

I tried the whole RAID 5,6 thing and realized that it is pointless and a waste of time (just my opinion). I use ZFS mirrors now (RAIDZ is the equivalent for your case). Rebuilds are sooo much quicker, and you can use multiple mirrors have thus have multiple backups. Of course, you need more drives. If you do not have enterprise class RAID cards, then I don't think running parity with all the issues it has is worth it.

My back up, for comparison purposes, is as follows:

1. Local (in same case as source).
2. External (can send to a friend's house, bank, etc). Can even do multiple externals. These in same filesystem as source.
3. I have an older Synology 2 drive model that I use for RAID 1 (why not, already have the unit)
4. NAS4Free ZFS
5. Cloud for family digital pictures as well (Google Drive)...but only for pics

As you can see, no RAID 5 or 6. This may seem like a lot, but it is EASY to administer and fast to do. Admittedly, there is more effort.

RAID is old technology, there are better options now (IMHO).

Good luck!

[SameSelf]

Wow, you just got three of us all saying the same thing. I think you know what to do now, right?

[ron spencer]

Wow, you just got three of us all saying the same thing. I think you know what to do now, right?

Well, the real point is that the OP can do whatever they choose. RAID is, however, no longer a panacea. For the corporate world with the bucks to spend on proper cards and RAID setups, sure. But for the home user on a consumer grade NAS (ASUSTOR NAS), I would not trust it. Too many easier and better alternatives.

That is, it is fun to tinker and have a massive drive show up on your system, at least until you need a rebuild.

[Chopmeister]

Yep. I think I have my answer.

It's mainly my media collection - I run a plex server on the NAS. So once stuff is added to the NAS it doesn't typically change.

I think that I will part it for a few months. In those few months I will order a bunch of 50GB DVDs and burn a complete duplicate backup to optical media (circa 240 disks is somewhat expensive and tedious, but not unreasonably so, if I do 2-3 a night). Then I will wipe the external USB drives and do a clean backup (it's a bit of a hotch-potch at the moment). After that I will either wipe the NAS and set it up as RAID6, or try an migration.

I know RAID isn't a panacea, but the NAS has worked reliably for nearly 3 years now. It is kind of nice to have all my media collection, searchable and with metadata, accessible to all the TVs and computers in the house. Which is why I will stick with it for a while yet - still 2 bays left for future volume expansion.

[ron spencer]

Well, if it is for media only and you have backups, then there is no real harm is using RAID, and you get the benefit of one large drive size to access. So why not? In my case, I have personal videos, software, pictures, etc that works well as I stated above in my plan. I have an older QNAP 4 drive unit that I use as JBOD for my media server. I may one day raid it to level 5, but I will have a backup for sure.

You are lucky that you have 5 bays and can expand to level 6 (double parity), so you can survive a rebuild crash better than level 5.

But again, don't try to fiddle changing your RAID level without blowing it away first...too many headaches. Let us know how you get on!

[SameSelf]

Yep. I think I have my answer....I will order a bunch of 50GB DVDs and burn a complete duplicate backup to optical media (circa 240 disks is somewhat expensive and tedious, but not unreasonably so, if I do 2-3 a night).

I also backup to dual layer BD-R (not DVD as you mention). Just be prepared that it will take a looooong time. My average time to master a single BD-R exceeds an hour. That includes prepping the files to be written (I always run checksums), time to to burn at 4x, and time to verify. But I do all this because the BD-Rs become my offline master video file archives. Fortunately, it is not really that expensive. If you already have a BD burner, a 50 disc spindle goes for about $100 on Amazon which works out to about $0.045/GB assuming you don't fill each disc 100% (I always leave at least 5% empty) which is on par with hdd costs (unless you buy cheap, crap drives) and actually conforms to data retention audits. My hope is triple layer BD-R prices eventually drop below $0.05/GB.

For your purposes, since you are not doing this as an archive (or are you?), it would probably be infinitely faster and easier (and even cheaper if you sell the drives on ebay afterwards) to just buy a handful of 4 TB drives as temporary storage to build your new NAS.

[Krispy Kritter]

I use additional HDD's as backup for important data. Never made the switch to Blu (and it's not time feasible nor cost effective to backup TB's of data onto disc), and DVD's don't go over 8GB.

[Chopmeister]

@Sameself - sorry, I meant BDR not DVD (hence the 50GB reference). I'm OK with it taking a while. If I do two disks a day (start one running before dinner, one after) then I will be through it in about 4 months. I'm happy to chip away at it, rather than sit there all night maniacally burning disks as fast as I can.. And yes, it is an archive. It's basically my plex server, which has a huge number of TV shows and films that I have capped off my set top box over the last 10-12 years. Mostly using a DVD recorder, converted to MP4 by Vidcoder. Lately, I have been capping in HD (via HDFury + HD PVR).

It's a bit of a hobby with me, and I seem spend more time capping and encoding the collection than actually watching stuff (esp when the GF is away for work). Almost like the film enthusiasts version of stamp collecting I guess. So I'm not fussed if it takes a bit of time. The good news is it doesn't change much, once a film/show is in the archive it tends to stay there. While there is a lot of unwatched material (I add about 10 films and 8-10 TV episodes a week), it is kind of nice to be able to fire up Plex and (say) select unwatched comedies if I am in the mood for a laugh etc. As Stalin once remarked, "quantity has a quality all of its own"

the 4TB ebay option isn't really feasible. With shipping costs to and from New Zealand, I would spend more shipping the drives than they are actually worth.

Long term I have some friends who are also media enthusiasts. I suspect I may just give them a copy of my complete collection, and let them be my extra off-site backup.

[SameSelf]

Well then, by all means burn away. Like I said, I have archived all my master video files to DL BD-R. There is something quite satisfying knowing that I never have to worry about a hard drive crash, bit rot, etc.

[Krispy Kritter]

And you anticipate NOTHING changing on your storage in the 4 months that it takes you to create the backups?

Hobby or not, I would be looking and planning for a real "hands free" solution. This isn't just about creating a backup, but also about restoring the data when needed. Create another array of similar size (you could use disc spanning and it would only be 2 additional HDD's) and use backup software to mirror the storage array weekly or monthly. If there ever is a failure, you still have access to your data without spending another 4 months rebuilding the array from all of your BD discs. And you don't spend any time burning or reading numerous BD discs (240+?).

[SameSelf]

If members on this forum are permitted to obsess over TBC's, then why can't someone choose to back up their data to BD-R without criticism?

Suggesting that he create a second array of hdd's for backup/rebuilding is bollocks. As a temporary migration solution, perhaps, but even that is not without risks. However, the most foolhardy backup solution is one which employs the exact same technology. That is right. Don't back up your spinning rust with more spinning rust. That is foolish. He has 12 TB of data. There is almost a 100% chance a data set that large is infected with bit rot.

Archiving to BD-R is time consuming to be sure. That is why I mention tape in my first reply. The problem is tape drives are $$$$$ (although they will chew through 12 TB like child's play). BD-R is cheap, and the only compromise is the time to write and read. However, with a large enough data set, the incremental cost of tape can be justified if your time is valuable. Outside of BD-R and tape, I can't think of any other technology to back up that much data reliably.

[ron spencer]

If members on this forum are permitted to obsess over TBC's, then why can't someone choose to back up their data to BD-R without criticism?

Suggesting that he create a second array of hdd's for backup/rebuilding is bollocks. As a temporary migration solution, perhaps, but even that is not without risks. However, the most foolhardy backup solution is one which employs the exact same technology. That is right. Don't back up your spinning rust with more spinning rust. That is foolish. He has 12 TB of data. There is almost a 100% chance a data set that large is infected with bit rot.

Archiving to BD-R is time consuming to be sure. That is why I mention tape in my first reply. The problem is tape drives are $$$$$ (although they will chew through 12 TB like child's play). BD-R is cheap, and the only compromise is the time to write and read. However, with a large enough data set, the incremental cost of tape can be justified if your time is valuable. Outside of BD-R and tape, I can't think of any other technology to back up that much data reliably.

BD-R is susceptible to bit rot...who told you it wasn't? Some BD-R even have gone bad when stored in sleeves. BD-R, DVD-R, etc are not REAL optical media. They all use dyes that will go bad eventually. This is not pressed material. BD-R are obviously better than the older DVD-R.

Please don't propagate the myth that "spinning rust" is bad. It just isn't (ask google if you must). If you are REALLY worried about bit rot you will use ZFS with ECC RAM. But life is too short, just back up regularly with SOMETHING. Saying that BD-R is a panacea and "spinning rust" is poor is plain wrong and just foolhardy. BTW, 12 TB is nothing these days.

[SameSelf]

When/where did I say someone told me that BD-R wasn't susceptible to bit rot? (clue: it wasn't google) Putting words in someone's mouth is not a good way to debate.

Also, please don't propagate the myth that spinning rust is good. Bit rot is not about your threshold of worry like, gee, better not get on that plane, it could crash. Rather, it is about probability which is a function of the size of the data set. At 12 TB, the probability is close to 100% unless you have been running something like openZFS—he is running RAID.

Besides what does "ZFS with ECC RAM" have to do with migrating/archiving data? It is fine to suggest openZFS in place of RAID for his new NAS (q.v. my first reply), but that doesn't get him any closer to solving his problem of migrating/archiving. 12 TB may be nothing for you, but it clearly is for the OP. Why do you think he posted here? If you want to bring some suggestions to the discussion other than BD-R and tape, I am am sure he will be interested.

[ron spencer]

@SameSelf....stop smoking the dye on your BD-Rs...it's only backup...keep burning your rust to BD-R....the rest of us will have fun! Enjoy your dye in your rocking chair!

[SameSelf]

real grown up ron spencer, you must be a lot of fun irl.

[Krispy Kritter]

To me, this is more a matter of time spent, not only the estimated 4 months to create the initial backup, but also all of the changes that are likely to occur in the future ( and during the 4 months of the backups). A second set of HDD's is simply MUCH faster and easier.

The comments concerning "ZFS with ECC RAM" are related to your comments about bit rot and are a solution to that issue (for those that consider it an issue).

And even if we do assume that his current data already has bit rot, then the backup method won't make any difference. BD-R will just take a much longer to time to copy the bit rot from source to destination.

Personally, I don't care which backup solution is used. I was simply encouraging that he select a faster, more automated solution. There are much better ways for someone to spend their time.

[SameSelf]

To me, this is more a matter of time spent.......There are much better ways for someone to spend their time.

This is one of the reasons this forum is frustrating. Rather than discuss the technical merits of various solutions (this is the computer sub, is it not?), everyone wants to bring up their personal preferences and argue from those positions. Don't be a fascist.

As for bit rot, I am done discussing it.

[Chopmeister]

Guys, firstly it would be nice if we could keep it civil, and focus on the merits or otherwise of options.

Secondly, just to be clear, I already have the NAS backed up to spinning rust, using a collection of USB hard drives of various sizes. I'm looking for a second backup suitable for offsite cold storage to guard against one or more of those having gone bad when I need to restore. I'm planning to keep a database, which for each file shows the USB disk and the BDR it was backed up to (unless there is a better option that BDR)

@Krispy Kritter - sure, I will ad files in the four-five (or however many) months it takes me to do the backup. But this won't change the files I have already written to disk (mostly movies, tv episodes and MP3s etc). It will add new files, so I can just burn the additions to subsequent discs. Once I have dealt to the backlog, I figure I will only have to burn 3-5 disks a month, which isn't too bad. And if I index them, I can recover only the files I need until I have done a full restore.

@ron spencer - I thought only LTH BDRs used dyes and were prone to short lifespans, whereas HTL ones didn't use dyes and if stored properly could last quite a while? Or am I wrong on that?

[Krispy Kritter]

Fair enough. But again, it's time consuming, but if you are fine with that, that's all that matters. And all media has a shelf life, so for safety it will need to be periodically verified (which again will be a huge time issue). As when burning any media (for storage/backup), ensure you verify each burn and perform random read tests to ensure the discs are error free.

[ron spencer]

real grown up ron spencer, you must be a lot of fun irl.

I am...go back to being a fascist about your backup schemes (it suits you).

[ron spencer]

Guys, firstly it would be nice if we could keep it civil, and focus on the merits or otherwise of options.

Secondly, just to be clear, I already have the NAS backed up to spinning rust, using a collection of USB hard drives of various sizes. I'm looking for a second backup suitable for offsite cold storage to guard against one or more of those having gone bad when I need to restore. I'm planning to keep a database, which for each file shows the USB disk and the BDR it was backed up to (unless there is a better option that BDR)

@Krispy Kritter - sure, I will ad files in the four-five (or however many) months it takes me to do the backup. But this won't change the files I have already written to disk (mostly movies, tv episodes and MP3s etc). It will add new files, so I can just burn the additions to subsequent discs. Once I have dealt to the backlog, I figure I will only have to burn 3-5 disks a month, which isn't too bad. And if I index them, I can recover only the files I need until I have done a full restore.

@ron spencer - I thought only LTH BDRs used dyes and were prone to short lifespans, whereas HTL ones didn't use dyes and if stored properly could last quite a while? Or am I wrong on that?

CDs and DVDs use organic dyes...so they don't last long..some BD-Rs use this as well. If you can find a BD-R that uses a metallic dye then that should last quite a while, assuming they are stored PROPERLY. You would need to ensure this based on the source of BD-Rs.

Frankly I would not worry about BD-R. Use if as part of a regular backup if you like. I love ZFS in NAS4Free and I use it, along with other stuff. Use whatever BD-R you can find if you want. Bit rot won't start on the BD-Rs for a bit and in a few years back up tp BD-R again.

Just be sure you have a backup SOMEWHERE.

[SameSelf]

@chop, LTH DL BD-R doesn't exist for obvious reasons. HTL DL BD-R is rock solid. That's why FB uses it for cold storage. Ignore the FUD. As for other cold storage options, spinning rust isn't one, but you seem to already know that, so fortunately no need to debate that. The only other option for cold storage that I am aware of is tape. And because it is backward compatible, you don't have to worry about an LTO-15 drive from the future not being able to read an LTO-5 tape if you use LTFS. And if you mine ebay, you can usually get a used tape drive for a few hundy.

So tape and bd-r. Those are the only two cold storage techs I would trust my data to. However, if only dealing with a few hundred gigs of data, or even just a TB or two, I would choose BD-R over tape due to cost. But you also need to factor in how fast your data is growing—maybe it is 2 TB now, but in a year will be 4 TB—well, at some point, tape becomes more cost effective both in terms of time and money. Also, 50 GB is kind of a hassle at times. It doesn't happen very often, but occasionally I have a file that is larger than 50 GB. Not a problem with LTO-5 which btw is the minimum gen I would recommend due to O/S support, etc.

Given that you have 12 TB of data which will require months to send to cold storage, I would take a serious look at tape.

Sadly, there just aren't many options for cold storage except for maybe a slab of stone and a chisel.