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Disk arrays for mixed sizes of disks

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kevinmcdonough View Drop Down
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    Posted: 03 January 2018 at 2:31pm
hey

Have had a couple of Drobo arrays over the years, and for the most part they've been great. Mixing and matching different sizes of disks as you upgrade is great, and their raid system means that even with a hard disk failure or two over the years, I've never lost any vital data. 

However I find that they are SUPER twitchy about drives, and will often mark a drive as unsafe even though it runs totally fine when plugged into a PC and scanning it with several software programs, including Spinrite, marks it as totally fine. 

On the one hand I suppose it's good that it's extra careful and sensitive about what drives it uses and minimises failures, but on the other hand I literally have a pile of like 12 drives of mixed 1, 2 and 3tb sizes lying on a shelf gathering dust as the Drobos reject them. 

Would love to move everything over to another brand's single big array, 8 or 12 disk maybe, that can use mixed drive sizes like a drobo so I can use up some of these other drives. Must do Raid 5 or 6 for protection against failures, but other than that i'm pretty flexible and happy to look at different options.

Any recommendations?

K


Edited by kevinmcdonough - 03 January 2018 at 2:31pm
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spongebob View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote spongebob Quote  Post ReplyReply Direct Link To This Post Posted: 03 January 2018 at 2:52pm
What disks? Consumer or NAS or enterprise?

If the SMART data on the drives is fine I would suspect TLER issues (or manufacture equivilent)

Best bet is:

Record SMART data of drive after drobo spit it out
Hammer it with one or two DBAN DOD runs
Compare SMART data and if the same as first reading insert back into drobo
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kevinmcdonough View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevinmcdonough Quote  Post ReplyReply Direct Link To This Post Posted: 03 January 2018 at 4:05pm
Just consumer grade drives for the most part, they've just been drives for my own personal document storage and for ripped DVDs and TV shows etc that I've built up over the years. Had three 4 drive drobos running at one point, through down to 2 now with larger drives. 

To be fair, overall they've been great. One is still a Gen 1 and one a Gen 2 so both pretty old now and still plugging away. Just annoying having to spend £60-80 to replace a drive every time it spits out what are seemingly fine and usable HDDs. 

Will give your suggestion a try with the newest 3tb I bought that's been rejected and see if it helps any. 

K
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Post Options Post Options   Thanks (0) Thanks(0)   Quote spongebob Quote  Post ReplyReply Direct Link To This Post Posted: 03 January 2018 at 4:57pm
At home now so able to type a more sensible reply!

Basically, in a "consumer" drive which is envisaged to be used in a desktop computer, if the computer issues a read/write request to the disk and something goes wrong, the firmware in the disk is designed to take an extra bit of time to try as much as possible to be able to service the read/write request, rather than spit an error back to the OS. Usually this extra unexpected time is OK because if 1 request out of say 1000 takes 500ms instead of 50ms, who's going to notice?

When the disk is attached to a RAID controller, essentially the disk should be "dumb"; any errors that occur should be dealt with minimally by the disk and the RAID controller will deal with the rest.

The result of attaching a consumer disk (in a firmware sense, there's alot to be argued about with regards to the hardware differences of a consumer/NAS/enterprise disk) to a RAID controller is that the disk can often do things it considers sensible, but the RAID controller doesn't.

Granted in the drobo this is all software RAID, but I suspect the same principles apply

Some hard drive manufacturers will allow you to "tune" the maximum time a drive will take to recover from an error before reporting it to whatever it's attached to, this might help in your circumstance
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Guests View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 03 January 2018 at 9:19pm
Raid 5/6 with disk sizes as they are nowadays is actually quite dangerous as you will hit the manufacturers "read error rate" very quickly
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nickyburnell View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nickyburnell Quote  Post ReplyReply Direct Link To This Post Posted: 04 January 2018 at 8:41pm
Knew most of this but not all. Very informative chaps Thumbs Up

Do the same principles apply in software raid though? 

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