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15TB HDDs: Western Digital Unveils the Ultrastar DC HC620

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Re: 15TB HDDs: Western Digital Unveils the Ultrastar DC HC620

#61

Post by blihp »

johngalt wrote: post #53
blihp wrote: post #48

Earlier quoted context omitted.

In the same way that hard drives didn't kill off tape, SSD won't kill off hard drives. The price differential is too great for many applications and they have different operational strengths and weaknesses.

Tapes have a use case that hard drives do not. Tapes are the lowest cost/GB stored and are more shelf stable than hard drives. SSDs are higher performance than HDDs and have none of the packaging constraints. Flash storage is going to be put into everything and the economies of scale look quite good. Storage is scaling but the r/w speeds of hdds aren't keeping up. Following the trend line and we see huge hdds that ar…

You state that with an unwarranted degree of certainty. You're making the same argument, and mistake, that proponents of 'X is going to kill hard drives' have made for decades.

There have been many 'this will be the death of hard drives' technologies over the decades: zip drives, optical drives, tape drives (there was a time when they were predicted to be everywhere... never happened), CD (then DVD) writers, etc. Not to mention MRAM which has been the hottest tech that hasn't really happened yet for 3 decades. These were all going to be some combination of more durable and/or cheaper per Xb. But they all lacked the one critical advantage that hard drives had: massive economies of scale. Here's my prediction: spinning rust isn't going anywhere anytime soon.

Re: 15TB HDDs: Western Digital Unveils the Ultrastar DC HC620

#62

Post by throwaway2048 »

StillBored wrote: post #52
throwaway2048 wrote: post #30

Earlier quoted context omitted.

as opposed to raid 5 where if any two disks fail your array is toast, raid 6 increases this to 3. However both raid 5 and 6 have 2 huge problems: Data inflight at write time (power/hardware failures are more likely to corrupt the array, especially silently, which is the worst outcome). Parity calculations require you to spin up the whole raid5/6 array during a rebuild, massively increasing the chance of a multi drive…

Data inflight at write time (power/hardware failures are more likely to corrupt the array, especially silently, which is the worst outcome). How is that? RAID doesn't affect data persistence behavior in any meaningful way. FUA/SyncCache/etc are supported by RAID controllers same as the underlying disks in writeback enviroments, parity updates included. Put another way, if you FUA or flush the writeback cache, those o…

Raid 5/6 require parity calculations before data can be written to disk. This is a significant amount of data, especially at high writing speeds. That is what causes the inflight data problem.

Battery and flash backup on controllers dosen't fix the problem of hardware failure (which is significant, especially on big hot controllers.

Re: 15TB HDDs: Western Digital Unveils the Ultrastar DC HC620

#63

Post by yellowapple »

chrisper wrote: post #23
stephengillie wrote: post #21

Earlier quoted context omitted.

This is one reason why RAID 0+1 is a best practice, and RAID 5 & 6 are no longer recommended. It takes too long to rebuild the array, leading to a multi-failed disk situation.

Raid 01 has its own risk. If the wrong two disks fail your entire array is toast

The normal answer here is to make sure that each side of the RAID10 (RAID01 is something different and much less common) mirror uses drives from a different vendor, thus giving each side a different bathtub curve / failure rate and mitigating the impact of a bad batch. This is a nice advantage over parity-based setups like RAID6 (since replicating this with RAID6 would require finding a unique vendor for each array member, and there are only so many vendors).

For archival purposes, though, you're probably better off with a normal RAID1 + some kind of JBOD setup (like with LVM); striping makes data recovery more difficult should you indeed lose all RAID1 sides of a given member.

Re: 15TB HDDs: Western Digital Unveils the Ultrastar DC HC620

#64

Post by astrodust »

orf wrote: post #15
chrisper wrote: post #2

It's an SMR drive. So better for archiving than regular IO

https://en.m.wikipedia.org/wiki/Shingled_magnetic_recording for anyone else wondering

Not to be confused with ASMR: https://en.wikipedia.org/wiki/Autonomous_sensory_meridian_re...

Re: 15TB HDDs: Western Digital Unveils the Ultrastar DC HC620

#65

Post by astrodust »

stephengillie wrote: post #35
chrisper wrote: post #23

Earlier quoted context omitted.

Raid 01 has its own risk. If the wrong two disks fail your entire array is toast

Multiple "0" drives can be added for further redundancy.

"Zero" drives are the ones that when you lose them you have zero data.

"One" drives are the ones with a copy.

Re: 15TB HDDs: Western Digital Unveils the Ultrastar DC HC620

#67

Post by astrodust »

aidenn0 wrote: post #44
worldexplorer wrote: post #38

Earlier quoted context omitted.

How do people use such large HDDs when internet download speeds are still low as compared to downloading directly on cloud services (like aws)?

My dad and I created backups locally, mailed each other hard-drives, and we just do a weekly rsync. Storage is large, but network traffic is relatively low.

Having a "backup buddy" you can swap drives with once in a while is never a bad idea. Encrypted backup drives can save your bacon if you're ever caught in a bad situation.

Re: 15TB HDDs: Western Digital Unveils the Ultrastar DC HC620

#68

Post by yellowapple »

worldexplorer wrote: post #38
bitL wrote: post #18

I was about to buy 3x 12TB Toshiba for Deep Learning datasets; now I need to reconsider... Does anyone know what are the current reliability stats for >10TB drives? My old 6x 4TB HGST in NAS are running without a single problem for the past 3 years...

How do people use such large HDDs when internet download speeds are still low as compared to downloading directly on cloud services (like aws)?

Over a scale of a few years, things add up.

Re: 15TB HDDs: Western Digital Unveils the Ultrastar DC HC620

#69

Post by StillBored »

throwaway2048 wrote: post #62
StillBored wrote: post #52

Earlier quoted context omitted.

Data inflight at write time (power/hardware failures are more likely to corrupt the array, especially silently, which is the worst outcome). How is that? RAID doesn't affect data persistence behavior in any meaningful way. FUA/SyncCache/etc are supported by RAID controllers same as the underlying disks in writeback enviroments, parity updates included. Put another way, if you FUA or flush the writeback cache, those o…

Raid 5/6 require parity calculations before data can be written to disk. This is a significant amount of data, especially at high writing speeds. That is what causes the inflight data problem. Battery and flash backup on controllers dosen't fix the problem of hardware failure (which is significant, especially on big hot controllers.

Again, decent controllers have ECC protection and the like, and frequently are available in HA configurations if your worry is controller failure (along with redundant/dual data paths to the media via SAS/NVMe/etc). Plus, there are a long list of technologies that can be enabled at the HBA layer and pushed all the way to the media (T10 DIF/DIX comes to mind).

But much of this micro level redundancy is overkill as frequently one uses some kind of application level HA/redundancy as well. So, loss of a RAID5/6 disk in a single machine is the functional equivalent of loss of a any combination of RAID 0/1 in the same machine. You still need the higher level redundancy as well as a backup plan.

We could start breaking the discussion up into fabric attached vs direct attach RAID vs Software, but I think its sufficient to say, that RAID5/6 doesn't _increase_ the failure surface in any meaningful way when your not using fly-by-night RAID.

Edit: Maybe what your trying to say is that cache flush/FUA operations for a give piece of data don't cover the parity calculation and buffers? That is false, a controller should not be responding to FUA/etc until the entire (including the parity) block has been persisted. So if the controller dies during the operation the host OS is fully aware that the operation didn't complete. The given block is of course left in some unknown state in this case, but that is true of any write operation that fails like this, regardless of WT/WB/RAID/etc.

Re: 15TB HDDs: Western Digital Unveils the Ultrastar DC HC620

#70

Post by simias »

aidenn0 wrote: post #45
simias wrote: post #31

Earlier quoted context omitted.

For archival spinning rust is still massively more cost effective than SSDs while offering better performance than tape, especially for random access. I'm sure eventually SSDs will be cheap enough that HDD will go the way of the floppy but we're not there yet.

Is tape even cheaper than spinning rust? Last time I priced it, the per-GB costs were similar and the tape drives themselves are quite expensive. Tape is a more reliable backup, since the moving parts are not part of the storage, but it's not a cheaper backup.

You might well be right, I haven't bought tape in a long time.
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