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Few questions after take off.


shteud

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Hello all!

I  just about 1 week ago from an end of the trial period of unraid. 

I should say i like a result.  But i have few questions on which i don't have answers (maybe i dig, not so deep :))

I plan to use this setup for home NAS/VM server. Before this, many years i use Windows server (2008/2012).

But at end, it's too heavy system for a home.

So I'm here  

I'm already doing some testing with freenas, now is unraid turn :)

Few things i can't understand:

1) read speeds. Do i get right what read speeds bottlenecked by the speed of single HDD which for storage?  SDD can't enhance its speed(of course i talk about flushed data).

2) Data protection. How much DATA disks from array i can be lost and repair (i don't talk about parity disks). for example, i have array 2(parity)+6(data) disks. how many disks from this 6 can i lost and repair?

3) Do there any sense to use hardware raid controllers with onboard cache (in it-mod) for HDD connection in case of unraid? Or simple HBA controller is preferred? 

4)Do it a good idea to use sdd pool (in mirror mode) from two pretty different drives(120 GB old (fat mlc) + 120 GB fresh (3D TLC) with not same RW speeds)?

I bee thankful for any help.
(small disclaimer. I'm not a native english speaker, so please be patient :))

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34 minutes ago, shteud said:

1) read speeds. Do i get right what read speeds bottlenecked by the speed of single HDD which for storage?  SDD can't enhance its speed(of course i talk about flushed data).

 

The data isn't striped. The disadvantage is that the read speed is limited to single-disk speed. The advantage is that when using the system as media store, it's enough to keep one single disk spinning when looking at a movie. And if you have a large failure, then every single disk contains a stand-alone file system allowing the files on the individual disks to be accessed.

 

35 minutes ago, shteud said:

2) Data protection. How much DATA disks from array i can be lost and repair (i don't talk about parity disks). for example, i have array 2(parity)+6(data) disks. how many disks from this 6 can i lost and repair?


The standard rule for systems with parity - one disk (any data or parity disk) per parity disk. So with single parity, you can recover from one broken disk. With dual parity you can recover from two broken disks.

 

36 minutes ago, shteud said:

3) Do there any sense to use hardware raid controllers with onboard cache (in it-mod) for HDD connection in case of unraid? Or simple HBA controller is preferred? 

 

Not so much need since each disk has a stand-alone file system. So the system is more robust in case of a power loss - in a striped system, you can have much worse file system failures when the same file system is spanned and different disks get different amounts of the file system changes.

 

38 minutes ago, shteud said:

4)Do it a good idea to use sdd pool (in mirror mode) from two pretty different drives(120 GB old (fat mlc) + 120 GB fresh (3D TLC) with not same RW speeds)?

 

Depends on what your needs are. If running Docker containers or VM on the cache drives, then it's definitely a good idea to use mirrored SSD so you get hardware redundancy.

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6 hours ago, shteud said:

1) read speeds. Do i get right what read speeds bottlenecked by the speed of single HDD which for storage?  SDD can't enhance its speed(of course i talk about flushed data).

 

Yes - typically read speed is gated by the speed on the single HDD you are accessing. The speed is based on the rotational speed + the data density. A 7200 RPM 12TB drive will be considerably faster than a 5200 RPM 2T drive (and even faster than 7200 RPM 2T drive). By faster I means sequential read and write speeds.

 

6 hours ago, shteud said:

2) Data protection. How much DATA disks from array i can be lost and repair (i don't talk about parity disks). for example, i have array 2(parity)+6(data) disks. how many disks from this 6 can i lost and repair?

 

2

 

6 hours ago, shteud said:

3) Do there any sense to use hardware raid controllers with onboard cache (in it-mod) for HDD connection in case of unraid? Or simple HBA controller is preferred? 

 

Although HBAs are normally best, there are times a RAID card, in addition to the HBA, can be helpful. My parity disk is actually a RAID0 volume from my Areca HW RAID card. This has two adavantages - 1-The disk is faster due to the striped RAID0 architecture, and 2 - I am able to economically repurpose a pair of smaller drives for parity. So I am able to buy a single new larger disk, repurpose 2 smaller drives as parity, and add the new large disk to the array taking advantage of its full capacity. Without a HW RAID card, you'd have to buy 2 larger disks to see value. I actually consider both of these to be very worthwhile. Note that unRAID does not work with all RAID cards. The Areca are the only ones I know are compatible. Some features don't work (unRAID can't spindown RAID volumes), but the RAID card includes configurable spindown features that work quite well so this is not really a serious limitation. Do some research if  you buy an Areca controller. There are some settings you need to use.

 

6 hours ago, shteud said:

4)Do it a good idea to use sdd pool (in mirror mode) from two pretty different drives(120 GB old (fat mlc) + 120 GB fresh (3D TLC) with not same RW speeds)?

I bee thankful for any help.
(small disclaimer. I'm not a native english speaker, so please be patient :))

 

I find SSDs to be quite reliable, and backup files to the array that I want extra protection. I have not experimented with cache pools. With your configuration you would likely get the read and write performance of the slower SSD. But not 100% sure - it depends on how smart is the BTRFS pool.

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4 hours ago, SSD said:

A 7200 RPM 12TB drive will be considerably faster than a 5200 RPM 2T drive (and even faster than 7200 RPM 2T drive).

 

You mixed up the order for 5200 and 7200 RPM 2 TB drives.

 

7200 RPM 12 TB is faster than a 7200 RPM 2 TB drive which in turn is faster than a 5200 RPM 2 TB drive.

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Thanks, guys for helping!

Ok so if i all correctly understood.

A zfs raid- z2 pool (from same 8 disks)can have much faster read speeds? But write speeds in zfs be much slower (because i can't use ssd as cache buffer)?

Why i ask about speeds. I plan upgrade my network to 10GE. So it been good to have opportunity utilize this speeds with hardware.

So it seems like for unraid, right way for build, use large ssd cache (in the mirror mode, for redundancy) and a longer time for flushing date on the array? (or maybe there is some kind of settings which make data stay in cache, even after data moved ot array (until new data overwrite existing?)

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8 hours ago, pwm said:

 

You mixed up the order for 5200 and 7200 RPM 2 TB drives.

 

7200 RPM 12 TB is faster than a 7200 RPM 2 TB drive which in turn is faster than a 5200 RPM 2 TB drive.

 

I said that a 12T 7200RPM was considerably faster than a 5200 2T drive, and it is also faster than a 7200RPM 2T drive. Trying to highlight that even if the rotational speed is the same, the speed of the drive (sequential read/write) still increased with larger drive. I didn't mix up the order.

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8 hours ago, shteud said:

A zfs raid- z2 pool (from same 8 disks)can have much faster read speeds? But write speeds in zfs be much slower (because i can't use ssd as cache buffer)?

zfs can use the ssd cache. zfs is probably the speed king if you are looking for fastest. There are plenty of other reasons why unRAID is popular, but speed is not one.

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15 minutes ago, c3 said:

zfs can use the ssd cache. zfs is probably the speed king if you are looking for fastest. There are plenty of other reasons why unRAID is popular, but speed is not one.

 

Cache only shares with SSD cache drives are quite fast. Cache pools add redundancy. But for a large library of media files, unRAID gives very good read performance (gated only by the speed of the disk and network). Redundancy is very economical. Write performance is impacted for the real-time redundancy, but is in the "fast enough" range for most users (normally 45MB/sec - 75MB/sec). And turbo write mode can be turned on to increase the write performance when needed. SSD arrays would represent a sizable write speed advantage if that is the primary need.

 

Although I would agree that unRAID is not the "fastest", I would say that there are a variety of features available in unRAID to allow good to excellent performance depending on the requirements and how you spec and configure the array.

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1 hour ago, SSD said:

But for a large library of media files, unRAID gives very good read performance (gated only by the speed of the disk and network).

 

The read requirements when consuming a media file are quite low.

 

 

For media data, it's normally when doing batch-processing (many media file processed at multiple real-time-speed) or when doing library indexing (a need to access a huge number of files) that read speed - or read operations per second - will matter.


And since the data isn't striped, a large unRAID media server may often stream from multiple disks ending up being network-limited instead of disk-limited.

 

In the end, it's normally for write operations or when running VM or Docker applications that sustained transfer rate or operations per second may end up too low with HDD accesses in the array.

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56 minutes ago, pwm said:

 

The read requirements when consuming a media file are quite low.

 

 

For media data, it's normally when doing batch-processing (many media file processed at multiple real-time-speed) or when doing library indexing (a need to access a huge number of files) that read speed - or read operations per second - will matter.


And since the data isn't striped, a large unRAID media server may often stream from multiple disks ending up being network-limited instead of disk-limited.

 

In the end, it's normally for write operations or when running VM or Docker applications that sustained transfer rate or operations per second may end up too low with HDD accesses in the array.

I manage  5+PB of storage for media files (Quantum and Primestream) and unRAID is not in the game for read or write speed requirements.

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3 hours ago, c3 said:

zfs can use the ssd cache. zfs is probably the speed king if you are looking for fastest. There are plenty of other reasons why unRAID is popular, but speed is not one.

For my use scenario, i think i can't get any benefits from L2ARC cache in zfs (i don't have a lot of such repetitive reads from the array in my home use).

 

2 all 

what about unraid cache tuning? do it's possible somehow make data stay in ssd memory even after flushing to disk array?

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54 minutes ago, c3 said:

I manage  5+PB of storage for media files (Quantum and Primestream) and unRAID is not in the game for read or write speed requirements.

 

But the general case is that when the requirements are special, you normally always need special solutions. And then special planning for how the data is distributed. So miles away from general-purpose solutions intended for SOHO use.

 

It's not very common that a single media stream needs more bandwidth than a single disk can handle. And if you need many concurrent streams, then it's better with a design where individual streams can come from individual disks instead of having a super-striped solution that gives a gigantic bandwidth for a single file but has to handle a huge number of seeks to jump between the different streams. And obviously a solution where popular media files are stored on SSD caches with no mechanical seek costs.

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Hello, All again.

So, i make a purchase on unRaid (basic edition) a few weeks ago. 

This few weeks all looks fine but today i got a white screen with "502 bad gateway"  problem and after rebooting the system, 

i got message "USB drive read-only mode" O_o

I don't do nothing to it. USB is brand new SanDisk 16gb i bought about 1,5 months ago.

Is this mean the drive is dead ( i cant install preclear utility,  which disappears after reboot)?

Is there any additional utility for USB disk check? 

What should i do?

 

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First off pull the USB drive and place in another machine and do a file system check. And at the same time make sure you have a backup of the configuration directory on the flash. It might even be good to try to make that backup before removing the device from unRAID in case there is a file system error where you can't mount the device after removal.

 

Another thing - consider how you have configured the system. You should normally have almost no writes to the flash - might you have something incorrectly configured?

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  • 3 weeks later...
On 7/19/2018 at 9:43 AM, pwm said:

First off pull the USB drive and place in another machine and do a file system check. And at the same time make sure you have a backup of the configuration directory on the flash. It might even be good to try to make that backup before removing the device from unRAID in case there is a file system error where you can't mount the device after removal.

 

Another thing - consider how you have configured the system. You should normally have almost no writes to the flash - might you have something incorrectly configured?

sorry for a long response. 

have no time for unraid repairing :(

I try to check USB on other pc. it just keeps saying "The media is write protected" :(  

I have no ideas why it's happening O_o  I don't do anything with usb (at least as i remember) i only hide USB from sharing in a home network.

I try to delete write protection with diskpart utility. it's not helped.

Any ideas?  Unraid mostly works fine (just can't update anything).

 

 

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9 minutes ago, itimpi said:

Assuming that you have not managed to set a switch on the USB stick into the ‘lock’ position, then a USB stick going into a read-only state is a typical symptom of a USB stick that is starting to fail.

it seems the only way to try a format and try check USB?

or it's not worth spend time on this? and just better go buy a new usb ?  (hehe :) its nice unraid start with buying new USB key after a few weeks after purchase)

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Two reasons for the drive being read-only.

 

Either the file system is broken, in which case the OS do not want to write to the drive to not destroy it more.

 

Or the flash memory on the drive is bad, in which case the memory controller don't want to perform writes because it does not have any flash blocks that can trust.

 

You can try to reformat the drive and see what happens - but there is a significant probability that the drive is failing.

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34 minutes ago, shteud said:

I see. Not good anyway. 

Ok i try format disk. (but how i just say it's write protected   ? )

But if this doesn't help wich vendor USB i can buy? Now i use sandisk. Can i use for unraid Samsung usb?

 

If it's read-only because of a corrupt file system, then it's the OS that made it read-only and it's possible to format the drive.

 

If the flash memory controller inside the drive made it read-only because of bad flash blocks, then it's probably not possible to reformat.

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Thanks all for help and support :)
OK. I changed the USB drive to a new drive from Kingston (I suspect the old one was out of order because of overheating, so I take a drive with big case). 
What settings do I need to make sure that it does not wear out in the future? 
And how often do I need to do parity check of main pool? Now it occurs once a day.
  Where can I see the SSD cash pool (2x SSD) settings?

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42 minutes ago, shteud said:

What settings do I need to make sure that it does not wear out in the future?

The default settings should be fine.

 

43 minutes ago, shteud said:

And how often do I need to do parity check of main pool? Now it occurs once a day.

Once/month might be a good choice.

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