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ZFS: Use mirror vdevs, not RAIDZ

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Re: ZFS: Use mirror vdevs, not RAIDZ

#111

Post by denkmoon »

tjoff wrote: post #25
necheffa wrote: post #24

Earlier quoted context omitted.

Repeat after me: RAID is not a backup solution, its an uptime solution.

RAID is not a backup solution, its an uptime solution. I know. Doesn't change the fact there exist no sensible way to backup a decently sized pool in a home-user scenario. Now we might disagree on what is sensible. And some things might not need a backup.

How can there be any sensible way other than having a complete copy of the data separate from the original copy?

It can be expensive, so perhaps just prioritise what you actually need instead of backing up LATEST.MOVIE.2020.Remux.r250

Re: ZFS: Use mirror vdevs, not RAIDZ

#112

Post by denkmoon »

res0nat0r wrote: post #76
dsr_ wrote: post #33

Earlier quoted context omitted.

zfs send. Keep different filesystems for system backup, personal data, media storage, gross hoarding. Consider not backing up the media storage and gross hoarding filesystems. Targets: 1. That NAS off in the corner built from an old desktop. 2. rsync.net and similar. 3. your encrypted cloud backup service of choice, through an adapter. If the value of your data is less than the cost to protect it, you know it is disp…

Backing up TB's of data isn't cheap no matter what type of cloud backup solution you're picking unfortunately. I don't think most here want to spend $1000/year on backing up their entire NAS.

b2 backblaze is quite cheap.

Re: ZFS: Use mirror vdevs, not RAIDZ

#113

Post by aidenn0 »

myrond wrote: post #102
aidenn0 wrote: post #52

Earlier quoted context omitted.

I was running 3x 12 drive vdevs in raidz2 and write performance was terrible . We moved some data to a different machine and rebuilt as 18 mirrors. This was a long time ago (as in running on Solaris long time ago), so maybe things are better now.

Each 12 drive array would have an interesting physical block layout. What was your ASHIFT and what was your physical disk raw sector size because if you had a ASHIFT=9 you would have 5120k blocks, if it was a ASHIFT=12 you would have physical 40960 blocks. None of those line up well with zfs. Additionally if this was a long time ago the pool would have defaulted to ASHIFT=9 and if you added any 4K drives you could ha…

Ashift=9 native 512b sector drives

Re: ZFS: Use mirror vdevs, not RAIDZ

#114

Post by uRStillfree »

denkmoon wrote: post #111
tjoff wrote: post #25

Earlier quoted context omitted.

RAID is not a backup solution, its an uptime solution. I know. Doesn't change the fact there exist no sensible way to backup a decently sized pool in a home-user scenario. Now we might disagree on what is sensible. And some things might not need a backup.

How can there be any sensible way other than having a complete copy of the data separate from the original copy? It can be expensive, so perhaps just prioritise what you actually need instead of backing up LATEST.MOVIE.2020.Remux.r250

Yeah, this.

Keep personal media metadata and download it again, maybe, but back it up?

Better still, only store what you’ll watch and delete it.

I only backup scans of truly useful legal documents, photos go to the cloud.

Everything contemporary, disposable pop culture is “backed up” online from my perspective.

Re: ZFS: Use mirror vdevs, not RAIDZ

#115

Post by somehnguy »

segfaultbuserr wrote: post #95
somehnguy wrote: post #49

No thanks. I use raidz2. With mirror vdevs if you lose the wrong 2 drives you lose everything. I can lose any 2 drives and be totally fine. The probability of losing the wrong 2 drives at once is small, sure. But I would rather just not care about that probability. And I don't lose half my capacity, which for a home user (I don't have an unlimited budget!) matters a whole lot more than having the absolute best iops.

The original article already included a reply to this question. > But wait, why would I want to trade guaranteed two disk failure in RAIDZ2 with only 85.7% survival of two disk failure in a pool of mirrors? Because of the drastically shorter time to resilver, and drastically lower load placed on the pool while doing so. The only disk more heavily loaded than usual during a mirror vdev resilvering is the other disk in…

It’s not a question, it’s a statement and my opinion on the matter. I respectfully criticize that your comment isn’t helpful at all nor a counter argument and is therefore useless as well. Please read my comment more carefully next time.

Re: ZFS: Use mirror vdevs, not RAIDZ

#116

Post by fomine3 »

myrond wrote: post #102
aidenn0 wrote: post #52

Earlier quoted context omitted.

I was running 3x 12 drive vdevs in raidz2 and write performance was terrible . We moved some data to a different machine and rebuilt as 18 mirrors. This was a long time ago (as in running on Solaris long time ago), so maybe things are better now.

Each 12 drive array would have an interesting physical block layout. What was your ASHIFT and what was your physical disk raw sector size because if you had a ASHIFT=9 you would have 5120k blocks, if it was a ASHIFT=12 you would have physical 40960 blocks. None of those line up well with zfs. Additionally if this was a long time ago the pool would have defaulted to ASHIFT=9 and if you added any 4K drives you could ha…

This is huge thing (called "Slop Space") that I noticed after I bought all ZFS NAS parts!

It wastes much capacity by default if drive count is not ideal. IIRC use larger recordsize (1MB or above) and enable compression almost solves issue. I use default 128K recordsize for small files zvol for performance, and use larger recordsize for the rest of zvols.

https://wintelguy.com/zfs-calc.pl

Re: ZFS: Use mirror vdevs, not RAIDZ

#117

Post by mulmen »

ubercow13 wrote: post #79
mulmen wrote: post #57

Earlier quoted context omitted.

What’s wrong with rsync.net or tarsnap for backups?

They are extremely expensive.

Wow yeah I just did the math again and they are! Tarnsap is 10x S3 prices? I know the service does a lot but I thought it was a small margin on top of plain object storage.

Re: ZFS: Use mirror vdevs, not RAIDZ

#118

Post by justinclift »

denkmoon wrote: post #112
res0nat0r wrote: post #76

Earlier quoted context omitted.

Backing up TB's of data isn't cheap no matter what type of cloud backup solution you're picking unfortunately. I don't think most here want to spend $1000/year on backing up their entire NAS.

b2 backblaze is quite cheap.

Further useful info:

https://www.cloudwards.net/backblaze-pricing/

It does sound good. :)

Re: ZFS: Use mirror vdevs, not RAIDZ

#119

Post by justinclift »

Fnoord wrote: post #92
mnd999 wrote: post #58

Earlier quoted context omitted.

2) and 3) requires a decent broadband upload speed. Home broadband often doesn’t provide this.

Depends where you're from I guess. Its also just the first backup which takes a (long) while. If you got only 10 mbit upload, then you're able to upload 600 mbit per minute, or 36000 mbit per hour. Which is about 4500 mB/hour (or ~4,4 GB/hour). Which results in 108000 mB/day (or ~105 GB/day). Its about 3/4 of a TB a week. I'm glad I got 30+ mbit upload with my VDSL2. My first backups took ages (I got 5 TB with Jottac…

Bearing in mind that it's likely not practical to use 100% of available upload bandwidth for extremely long periods of time. Generally speaking anyway. :)

Re: ZFS: Use mirror vdevs, not RAIDZ

#120

Post by Dylan16807 »

Fnoord wrote: post #91
res0nat0r wrote: post #76

Earlier quoted context omitted.

Backing up TB's of data isn't cheap no matter what type of cloud backup solution you're picking unfortunately. I don't think most here want to spend $1000/year on backing up their entire NAS.

> I don't think most here want to spend $1000/year on backing up their entire NAS. These 2 solutions cost less than 10 USD/month: Jottacloud [1] and zfs.rent [2]. The former is even hosted in privacy-friendly Norway, and its 5 TB unlimited with going over that you get upload-capped. So I pay 90 EUR/year for Jottacloud. Which is approx 10% of your projected 1000 USD. [1] https://www.jottacloud.com/en/ [2] https://zfs.…

Jottacloud could be a useful offering, but someone considering the best way to balance many drives on a NAS and worried about spending $1000/year to back it up is probably not going to fit into a single account.

zfs.rent is an interesting model, though quite beta and currently not accepting users. And those prices add up pretty fast. Let's say you want to back up about 4 drives of data. That's $960 a year for the first two years, then $480 a year after. Or if you want any redundancy at all, $1200/$600. You'd probably want to find your own cheaper box to stuff hard drives into, and at that point you're far gone from "cloud".

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