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A lesson for all...

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dnar
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A lesson for all...

#1

Post by dnar » 12 May 2013 11:30

My son has been running a RAID5 array with 4 drives under Ubuntu.

Today his array failed, 2 of the 4 drives throwing tons of bad sectors. I suggested we replace all drives with new ones as they are now 4 years old, then we can restore his backup.

"What backup Dad? I didn't bother with backups as my data was on a RAID array!"

Lesson #1 - RAID is NOT a substitute for backups! Backup your data people!

Lesson #2 - RAID 5 can tolerate a single drive failure only, and Murphys Law says a second drive will fail IF you don't have backups.

Here endeth the lesson.
NAS 1: NAS4Free 9.3.0.2 x64 embedded, Intel Core 2 E8400, 8GB, 6 x WD Green 1TB in RAIDZ2, Highpoint 2720 SAS x 8 card 6Gbps
NAS 2: NAS4Free 10.2.0.2 x64 embedded, Intel Core i3-3220, 8GB, 7 x WD Green 750GB in RAIDZ1, onboard SATA 3Gbps

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Re: A lesson for all...

#2

Post by russian » 12 May 2013 18:46

That's pity.

Yeah, backups and backups everything again. Backup to other HDD, backup to other PC, and backup to other building.

Weak point of RAID5 is when one of disks is failed. In Reconstruction state RAID5 make a high load on other disks, and this could provoke their failure.

"There are three kinds of system administrators: first ones who don't make backups; second ones - who already make backups; and the third ones - who make backups, and check if they could restore from their backups" (c)
Nas4Free x64 9.2.0.1 rev.972; case: Lian Li PC Q08b; mb: ASUS E35M1-I; cpu: AMD E-350; mem: 4 Gb; hdd: 6xSATA

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Re: A lesson for all...

#3

Post by kkd » 13 May 2013 07:34

Dont forget: raid5 is slow. Use Raid10.
XigmaNAS x64-embedded | INTEL Intel(R) Core(TM) i3-2100 CPU @ 3.10GHz | 9216MiB RAM | X x YTB WD Red ZFS mirror compressed

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b0ssman
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Re: A lesson for all...

#4

Post by b0ssman » 13 May 2013 07:43

kiss.daniel wrote:Dont forget: raid5 is slow. Use Raid10.
soft raid 5 is not slow. for modern cpus the parity calculation is negligible.
Nas4Free 11.1.0.4.4517. Supermicro X10SLL-F, 16gb ECC, i3 4130, IBM M1015 with IT firmware. 4x 3tb WD Red, 4x 2TB Samsung F4, both GEOM AES 256 encrypted.

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Re: A lesson for all...

#5

Post by dnar » 13 May 2013 08:07

Yeah, soft RAID performance was very good. And, your not bound to a particular hardware controller.

I suggested he replace his 4 x 500GB array with a single Seagate 2TB drive, and offered him a 2TB quota on my NAS so he can backup nightly via rsync. This weekend I'll run CAT6 to his room for speed.

My RAIDZ2 NAS is backed up nightly to another RAIDZ1 NAS, and then monthly to individual USB drives.
NAS 1: NAS4Free 9.3.0.2 x64 embedded, Intel Core 2 E8400, 8GB, 6 x WD Green 1TB in RAIDZ2, Highpoint 2720 SAS x 8 card 6Gbps
NAS 2: NAS4Free 10.2.0.2 x64 embedded, Intel Core i3-3220, 8GB, 7 x WD Green 750GB in RAIDZ1, onboard SATA 3Gbps

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Re: A lesson for all...

#6

Post by siftu » 18 Jul 2013 05:53

b0ssman wrote:
kiss.daniel wrote:Dont forget: raid5 is slow. Use Raid10.
soft raid 5 is not slow. for modern cpus the parity calculation is negligible.
Maybe KKD was referring to the IOP penalty. I always liked these type of tables for that. http://www.yellow-bricks.com/2009/12/23/iops/

RAIDZ is even worse for IOPS as it touches all the disks to check the checksum.

But saying that, if you arn't running a database or vmware cluster on the thing, and all you are doing is streaming a few movies and doing backups.. Who cares.
System specs: NAS4Free amd64-embedded on ASUSTeK. M5A78L-M LX PLUS - AMD Phenom(tm) II X3 720 Processor - 8GB ECC Ram, Storage: 2x ZFS mirrors with 4x Western Digital Green (WDC WD10EADS)
My NAS4Free related blog - http://n4f.siftusystems.com/

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Re: A lesson for all...

#7

Post by ku-gew » 21 Jul 2013 01:47

If you build RAID10, buy two disks and make a RAID1. Then, a couple of months later, add two disks in two stages: the first additional disks will be used to make a 3-way RAID1 (you add it to the existing RAID1), then you take out one of the original disks of the RAID1 and with that one and the second additional disks you make the new RAID1 that will be striped with the previous one to have RAID10. This way each mirror will have disks bought about two months apart and the probability to have two failures at the same time is lower.
HP Microserver N40L, 8 GB ECC, 2x 3TB WD Red, 2x 4TB WD Red
XigmaNAS stable branch, always latest version
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Re: A lesson for all...

#8

Post by kkd » 21 Jul 2013 05:35

siftu wrote:
b0ssman wrote:
kiss.daniel wrote:Dont forget: raid5 is slow. Use Raid10.
soft raid 5 is not slow. for modern cpus the parity calculation is negligible.
Maybe KKD was referring to the IOP penalty. I always liked these type of tables for that. http://www.yellow-bricks.com/2009/12/23/iops/

RAIDZ is even worse for IOPS as it touches all the disks to check the checksum.

But saying that, if you arn't running a database or vmware cluster on the thing, and all you are doing is streaming a few movies and doing backups.. Who cares.
i do care. it's my data on my hdds. i never run dbserver on vm. i never force my cpu to count if i dont need so and mainly never force my hdd to write if it's really not needed. raid5 writes not just ur datas but far more taking away ur hdds lifetime. and if u restore because of 1 hdd died, u really force all the disks spin and cpus count like hell. all r just source of failure.

i think there is only one case u need to use raid5: u got really large amount of data, and u need to save space.
XigmaNAS x64-embedded | INTEL Intel(R) Core(TM) i3-2100 CPU @ 3.10GHz | 9216MiB RAM | X x YTB WD Red ZFS mirror compressed

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Re: A lesson for all...

#9

Post by ashlybranna » 19 Oct 2015 15:37

It's sad to hear, I'm sorry :( I had such situation too, now I aware. Last time I lost so much data, including paperhelp plagiarism checking program I wrote, and important tasks I needed for my study. So thanks for the thread, people need to know.

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Re: A lesson for all...

#10

Post by noclaf » 19 Oct 2015 16:10

kkd wrote:i think there is only one case u need to use raid5: u got really large amount of data, and u need to save space.
Which is why most of us is having N4F...I guess. :lol: 1TB of important stuff I can keep on my PC without need to build server. But I wish I had enough money to build 9TB storage like I have not using R5 but using R1. :P

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Re: A lesson for all...

#11

Post by kkd » 19 Oct 2015 16:41

noclaf wrote:
kkd wrote:i think there is only one case u need to use raid5: u got really large amount of data, and u need to save space.
Which is why most of us is having N4F...I guess. :lol: 1TB of important stuff I can keep on my PC without need to build server. But I wish I had enough money to build 9TB storage like I have not using R5 but using R1. :P
try lottery ;) I need no luck, I use raid1... But when u start crying because of lost data please reread above posts
XigmaNAS x64-embedded | INTEL Intel(R) Core(TM) i3-2100 CPU @ 3.10GHz | 9216MiB RAM | X x YTB WD Red ZFS mirror compressed

noclaf
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Re: A lesson for all...

#12

Post by noclaf » 19 Oct 2015 17:01

Don't worry about my tears. ;-) Photos and other important stuff I have redundatly saved on a different computer. Moviez, warez and other such stuff - I can live with losing it. I really consider having R1 for "SOHO" purposes an overkill. But if you like it...I'd rather spend the money on something more funny.

BTW - Raid 1 - very nice, much safer, so protected...but what if your PSU is going to have major failure taking into silicon heaven majority of your HDDs? :-)

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