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In RAID5, if 2 disks fail does one lose all data?

Say there are 250 4Tb drives and 2 drives fail does one lose all data of 250 drives?

How do data centers ensure continuous storage?

In a server where people can upload files if one drive is full files must shift to new empty one. Is it possible with RAID5?

Dave M
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rightlifesavecompenthusiast
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1 Answers1

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In RAID 5 if 2 disks fail does one lose all data.

No. One looses all the data that IS NOT BACKED UP.

How do data cente rs ensure continuous storage.

By not relying on RAID5 not to fail. RAID5 is there to handle an outage of a single disk - THAT'S ALL! They are quite common (though today running 4TB drives on RAID5 is restless - the limit is around 900GB for 10K Enterprise SAS drives, after that you want to run RAID6 or RAID10 or maybe RAIDZ2).

THEN you POSSIBLY mirror the data to another server or two. Azure IIRC keeps 3 copies of the data around.

THEN you do backups.

I had a RAID5 blow up in one of my companies main machines (actually THE main machine) years ago. We where back with a full restore down to the last relevant backup (which we do every 15 minutes) next morning.

You do NOT rely on RAID5 to save your data. It is just a "let's keep machines running if a disk fails" first line of defense.

BaronSamedi1958
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TomTom
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    Well, they use technology that exists longer than you likely live - backups are a problem solved for many years. At some point you end up with offsite tapes, you know. LARGE tape libraries. – TomTom Jul 01 '20 at 12:31
  • Yes, they backup their own stuff and offer backup systems to customers if they want it - also don't use R5, it's dangerous and has been for over a decade, stick to R1/10 or R6/60 ok, never trust R5 - also backup, RAID isn't a backup, ever. – Chopper3 Jul 01 '20 at 12:31
  • Also you wouldn't ever do a 240 disk R5, if it worked at all you'd be certain of losing your data, for arrays of that size you need a professional to help you. – Chopper3 Jul 01 '20 at 12:33