2*24TB RAID1 vs. 4*8TB RAID5

[Dirt Chip]

Case use: A new, cold storage, on a different PC, backup for an already existing 2*18TB RAID1 setup (on a work PC, see spec “silent sheep”) that hold a lot of raw video files, .DNG photos and finished projects.

I currently have backup on external HDD’s, but looking forward I want a more robust solution and a 3rd (as recommended) backup.

The new RAID backup will be placed in an old PC I have (see spec “dirt sheep”). It will be an offline (no internet) and un-plagued (except for when adding new stuff for backup). Probably win10 based.

I’m not ‘locked’ on the TB capacity, but 18TB is the very minimum and preferably more.

Where I live the cost for 2*24 and 4*8 is about the same so I will appreciate any options as hands-on experience as to what is better for the long run.

I’m less inclined for RAID6 because it will be a cold backup, so 2 disc failure is very unlikely to happen as far as I understand and the cost is greater for the same TB capacity , but open to here other though of course.

 

[Harlow]

I’m less inclined for RAID6 because it will be a cold backup, so 2 disc failure is very unlikely to happen as far as I understand

I run RAID-Z2 (equivalent to RAID6) under TrueNAS Core because there's a finite chance that when one drive fails, another drive might cause problems during the resilvering process. I have one 6-disk array and three 8-disk arrays in separate machines.

The TrueNAS and Serve-The-Home forums warn that buying all your RAID disks in one batch from one supplier, can lead to several failures in quick succession after a number of years service. Some batches of disks may have been badly manufactured. Disk firmware may not be 100% stable, leading to corruption/failure.

Above a certain number of drives, RAID-Z1 (RAID5) isn't considered "safe" enough, so additional parity is introduced, e.g. RAID-Z2 or RAID-Z3. Of course even three additional (wasted) drives will still not protect against all eventualities.

If you ask this question on Tom's Hardware, you'll immediately be asked "why RAID1"? Many years ago I had a RAID1 (mirror) setup and over time, both drives developed bad sectors. I split the array and recovered most files, but it served as a warning. The "experts" claim RAID1 is good for point-of-sale terminals where you need to continue using the computer until the store closes. RAID1 does not protect against accidental file deletion, ransomware, catastrophic PSU failure, etc.

If you use an OS like TrueNAS, you can scrub the drives periodically looking for "bit rot". If you use smaller capacity drives, they'll be less expensive to replace. The advantage of TrueNAS is you can move an array between different machines with ease. I pulled an 8-disk SAS array from an HP Xeon server with ECC RAM and installed the drives in a tower PC with standard CPU/RAM. If you use hardware RAID, you may have to replace the controller with an identical unit, if the board fails.

Where I live the cost for 2*24 and 4*8 is about the same so I will appreciate any options as hands-on experience as to what is better for the long run.

I'd opt for four 8TB drives, but how you arrange them is up to you. RAID is not a backup, but you've already got that covered. Data storage gets expensive.

I currently have backup on external HDD’s

I stopped using a large collection of WD and Seagate USB3 drives in 2018 and switched to LTO4 tape storage. Second hand SAS tape drives are cheap ($100) and I get 800GB on each tape. I shoot 600GB RAW/JPG files on holiday and they fit on a single tape. As archives, tapes are less likely to be infected by ransomware, especially when you slide the tab over to "write protect" making the tapes read-only. I'd probably opt for LTO5 or LTO6 now, but LTO9 is very expensive indeed.

 

[Dirt Chip]

Thanks for the info

As I see it:
RAID1 pros:
1- less drives in the PC- let me expend and add another RAID1 in the future with ease without adding PCIE add on cardswith SATA ports. RAID1 use 2/6 SATA ports, RAID5 use 3-4/6.
2- Each drive holds all data, so I can take 1 drive from the backup RAID1 out and put it in the work PC if I need to restor a larg quantaty of data (in case of 2 drive faliure\ransomware and such). As far as I understand you cannot do this with RAID5 setup.

RAID5 pros:
1- Cheaper HDD cost, so the initial setup will cost less if I go with 3 drives. also, cheaper to replace in case of a drive failure.
2- Smaller size HDD are more common, so less trouble finding a replacement HDD and even better- easier to find 3/4 different kinds of HDD`s to mix together and avoid bad batch

btw, if I do mix drives from different companies- what is important to notice?
I guess you must have same RPM but what about internal cache and other parameters? what is importent for a good HDD mix?
Are there (modern) drive you canno`t RAID1/5/6 nowdayes?

 

[Panther_Seraphin]

RAID5 I would be reluctant to use as a hard backup system. Most of the time if one drive has failed unless its really early on tends to mean the other drives are nearing the end of their life and a resilver/rebuild is one of if not THE most intensive operation on the physical drives. Too often a RAID 5 especially on extremely large drives will experience a secondary failure DURING the rebuild losing all data.

After a few years you are far better off to replace/upgrade the array then transfer the data off the drives then retire the existing drive into a non critical role.

 

[Red Hood]

Raid 1 is better for backup than Raid 5 (Raid 6 with smaller disks is recommended but works out more expensive)

Raid 5 is not great, especially with large disks and as Panther mentioned, they are prone to rebuild failures

Check the specs of the disks and make sure they are conventional and not shingled

 

[Dirt Chip]

Check the specs of the disks and make sure they are conventional and not shingled

Shingled? Can you elaborate what it is?

 

[ShiBDiB]

Raid1

Less points of failure for a backup system should always be the goal. KISS.

Also seagate has some fairly cheap refurbished ironwolves on their official ebay page if you're looking for reliable large hdd's. I grabbed two and was reminded how loud mechanical drives were and switched my NAS back to ssd's as it sits on my desk

 

[Chrispy_]

I run RAID-Z2 (equivalent to RAID6) under TrueNAS Core because there's a finite chance that when one drive fails, another drive might cause problems during the resilvering process. I have one 6-disk array and three 8-disk arrays in separate machines.

I use Z2/RAID6 for archive servers, combined with monthly RAID scrubbing.

RAID5 died when HDDs reached beyond about 5TB each. The capacity since then has quadrupled, but the rebuild rate has barely changed, increasing the array loss risk during a rebuild by a factor of 4.

 

[Red Hood]

Shingled? Can you elaborate what it is?

Shingled disks have data tracks that overlap like roof tiles, so more of them can be fitted in the same area resulting in higher capacity disks and are cheaper to make

They have lower write performance, sustained writes are not good and not suitable for raid arrays

 

[Dirt Chip]

Shingled disks have data tracks that overlap like roof tiles, so more of them can be fitted in the same area resulting in higher capacity disks and are cheaper to make

They have lower write performance, sustained writes are not good and not suitable for raid arrays

How can I tell which is which?
Dose it say or I need to understand it from the spec?

 

[Red Hood]

How can I tell which is which?
Dose it say or I need to understand it from the spec?

Some disks have it in the product name/description, some only in the spec

If it says SMR its a shingled disk

 

[Sol_Badguy]

How can I tell which is which?
Dose it say or I need to understand it from the spec?

CMR and SMR Hard Drives | Seagate US

See the list of recording technology utilized on our internal hard drives

www.seagate.com

https://storage.toshiba.com/internal-specialty-hdd/pc

Western Digital Support | Western Digital

Find detailed answers to your support questions for your Western Digital products.

support-en.wd.com

And so on.

CMR vs. SMR Hard Drive: Which One is Better to be Choosen？

CMR vs. SMR hard drives is two different types of data recording for mechanical hard drives. Both CMR vs SMR have their own pros and cons. It is important to tell the differences and know which one is better to be chosen for different purposes.

www.easeus.com

 

[Harlow]

I can take 1 drive from the backup RAID1 out and put it in the work PC if I need to restor a larg quantaty of data (in case of 2 drive faliure\ransomware and such).

If ransomware infects a RAID1 array, you'll lose both copies of any files encrypted by the virus. Just keep plenty of backups of important files in different locations, not all in the same machine or on the same LAN. I use FreeFileSync to keep folders in sync on different machines. Similar to the concept of RAID1, but more work is involved. You can automate folder/disk synchronisation or backup jobs, if you prefer an easier life. Relying on RAID1 to keep files "safe" is too many eggs in one basket for my liking.

Shingled? Can you elaborate what it is?

It's a cunning way to increase drive capacity without adding more platters. Manufacturers can squeeze another 5 to 10% storage out of a drive for "free" and sell it at a higher price, or undercut competitors' CMR/PMR prices.

SMR is OK if you want a cheap drive for archiving data, but not so good if you use the drive constantly.

After using a shingled drive for some time and deleted files, it takes much longer to write new files to the drive. Chances are, quite a few USB3 hard disks are shingled.

https://www.howtogeek.com/803276/cmr-vs.-smr-hard-drives-whats-the-difference/

A few years ago WD were found to have sneaked shingled drives into their Red NAS range. Very naughty. This was extremely bad news for anyone using ZFS operating systems (FreeNAS, TrueNAS). If you need to replace a failed drive and resilver a ZFS array, the task can take days instead of hours, or just time out a fail completely. Other (non ZFS) RAID systems are more tolerant of SMR.
https://www.servethehome.com/surreptitiously-swapping-smr-into-hard-drives-must-end/

How can I tell which is which?

There are plenty of web sites with the necessary info.
https://nascompares.com/answer/list-of-wd-cmr-and-smr-hard-drives-hdd/

I guess you must have same RPM but what about internal cache and other parameters? what is importent for a good HDD mix?

Ideally you should use identical drives in a typical RAID build, but you could build an array with different speeds (5400/5900/7200RPM) and different capacities. If you set up a 4TB 5400RPM drive and 6TB 7200RPM drive in RAID1, it should still work, but you'll leave 2TB unused space on the 6TB drive and the array will run slightly slower. A better use of different sized drives might be JBOD.

Another potential snag is when it comes to replacing a failed drive. Pick any capacity you can think of, then check the exact size (in MB) of various manufacturers' offerings. They could differ by a few tens or hundreds of Megabytes. The problem arises if when the replacement drive is slightly smaller than the other drives in the array. If your existing drives are 4.001TB but the replacement is only 3.999TB, you may need to fit a 5TB drive to rebuild the array. Alternatively, you could copy the data off the array, delete the array, rebuild it slightly smaller, then copy the data back.

a lot of raw video files, .DNG photos

Do you keep the original RAW photo files after converting to DNG? I shoot RAW + JPG and save on two separate cards in camera, then keep both sets of files. A waste of storage? I find H.265 more space efficient than H.264 after editing video. With care, I could save GB or TB of drive space.

 

[Chrispy_]

Shingled disks have data tracks that overlap like roof tiles, so more of them can be fitted in the same area resulting in higher capacity disks and are cheaper to make

They have lower write performance, sustained writes are not good and not suitable for raid arrays

Disks with shingles aren't much good for anything except low-bandwidth sequential stuff. It's why most of them are branded "surveillance" drives because the pitiful data stream of a few low-res, low-framerate CCTV cameras is about all they're capable of.

When buying disks for use in arrays, ensure you see the acronymn CMR somewhere on the spec sheet. If you see SMR, avoid it like the plauge, it will ruin your array and perform like tape drive from the 1970's

 

[Panther_Seraphin]

SMR are ok for mainly read operations so if its going to be mainly for linux ISOs/Photo/Video storage etc then they are fine but if its data that is going to be chopped and changed then SMRs are horrendous as every time you make an edit you arent just affecting that data track, you also make changes to the ones around it hence the absolutly horrendous random write performance on them.