On Thu, 4/10/2025 4:29 PM, Joe wrote:
On Thu, 10 Apr 2025 18:39:05 -0000 (UTC)
rob <rob@nospam.com> wrote:
Can anyone recommend a good reliable disk to use for cctv recordings.
My second WD disk has just failed after almost 2 years. The 1st disk
was a WD Blue, and this one is a WD Purple. Both have failed in less
than 2 years.
Just a comment, drives specifically for DVRs and CCTV do exist, though
of course cost a bit more.
As far as PC drives go, I've seen proportionally more failures from WD
that others, and in the very early days of hard drive video recording, Quantel used to use Fujitsu drives exclusively for Harry. Of course,
that was decades ago, I've had some Fujitsu PC drives but I don't know
if they're still in that market.
You'd probably do better trying to find a security forum, where there
should be plenty of appropriate experience.
But that's what a WD Purple is for, is multiple-CCTV-threads recording.
The WD Blue is a terrible choice, for any purpose, as it has
the most-crude voice coil control (for a relatively high density platter).
As far as I know, it would have an eight hour usage day, 110TB/year,
as a metric for wear characteristic. I don't think I have a spec handy
for it. If you "had to buy cheap", I'd tell you to get a WD Black instead,
as they're one level above the Norwegian Blue. I received a WD Blue in
a refurb computer and... had to replace it. There is a WD Black there now.
The drive was by itself, so it wasn't a vibration problem, which is what
most people would accuse you of.
The Purple should have been a bit better. It's 180TB/year so has
a higher rating than the Norwegian Blue. 3 year warranty. The WD Purple 3TB
(or larger) has 256MB cache. The lower capacity ones have 64MB cache.
Modern drives, the cache really works, and with NCQ tagging, the drive
can reorder writes to best suit the seek pattern. The computing device
writing to the drive, has to have AHCI to have the driver support for
tagging of commands. (SAS drives have really deep tagging, the SATA tagging
is more of a joke.)
The WD Gold is 550TB/year and is considered a "continuous duty" drive.
24 hours a day. It has multiple levels of actuator. A voice coil for
gross control. A piezo located near the head for fine control, and
a DSP and NRRO control to help null out the effects of vibrations
from adjacent drives. The WD142KRYZ is 14TB, helium filled (matters not
for wear characteristic), has a 512MB cache (bigger than a purple, but
not multi-thread optimized). It could still be multi-thread optimized
for server operation though. It's a 512e drive (your file system should
be aligned properly, not "formatted on WinXP" which would be a mistake).
The 512e drives do not do as well if MSDOS formatted by older OSes with divisible-by-63 numbers. And items like that (Enterprise server drives)
make a "thumping sound" during self test, which is quite frequent. They
don't go whole-hog and make the screeching sound that 15K RPM drives made
every 71 seconds, so they're not that weird. But they do still thump.
Warranty is five years.
Drives bigger than the 14TB, simply have more platters inside.
The platters on those are relatively thin, and the base material is
likely different (back to glass platters). There isn't much benefit
going to the 26TB model, except it has OptiNAND (writes the 512MB cache
to a NAND flash memory on emergency power fail, copies the NAND to
the disk when power is next restored). That allows the heads to be
parked immediately, without attempting to squeeze in any last-second
writes.
A rule of thumb, is drives in web servers, constantly doing random
seeks, the arm lasts about one year doing that. A CCTV recorder could
be moving constantly, but perhaps at a slightly lower rate-of-seek
(as the cache can queue up the stuff a bit for write). The multi-channel recorder can also help out, by increasing the size of segments recorded
for each camera, so the seeks per second are reduced a bit.
The Purple drive in this case, should really last more than a year.
*******
And a warning about the drives mentioned so far. SMR utilize
writes in 7 track chunks, and would be TERRIBLE for a CCTV recorder.
The poor drive would be saying stuff like "I'm drowning here, cut that out". SMR drives are only suited as backup image drives (continuous write
of a single 1TB file kind of thing). They would not like handling
small files. They're not NAS material for example, Not particularly
suited to RAID arrays. SMR writes of small quantities of data,
use Read-Modify-Write of 7 track chunks. You can see in this WD Blue
document, there are a couple turds in the punch bowl, to be avoided
(like, if there was a reason to be buying a WD Blue in the first place).
https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/internal-drives/wd-blue-hdd/product-brief-western-digital-wd-blue-pc-hdd.pdf
8TB 8TB 6TB 6TB 4TB 4TB
WD80EAAZ WD80EAZZ WD60EZAX WD60EZAZ WD40EZAX WD40EZAZ
CMR CMR CMR SMR CMR SMR
^^^ ^^^
Lemon Lemon
There was a stink, when some WD Red drives intended for NAS usage,
were discovered to be SMR inside (which won't handle write updates
well at all). Now, the parameter is more likely to be listed in a
datasheet, making it easier for customers to avoid such workmanship.
https://en.wikipedia.org/wiki/Shingled_magnetic_recording # Lemon, do not reward the industry by buying these.
https://en.wikipedia.org/wiki/Perpendicular_recording # perpendicular magnetic recording, PMR
# == conventional magnetic recording CMR
# This is the good kind. Bits stored vertically. 0.5 to 26TB currently.
https://en.wikipedia.org/wiki/Heat-assisted_magnetic_recording # HAMR \___ high capacity, expensive
https://blocksandfiles.com/2019/09/03/western-digital-18tb-and-20tb-mamr-disk-drives/ # MAMR / Not likely for home use (yet)
*******
Make sure you're aligning the file system properly on these drives.
If the recorder is "an ancient piece of crap", it could be
partially responsible for the bad behavior. Win7..Win11 have
1MB alignment and power-of-two alignment which works well
with 512e (4K internal sector) hard drives. Drives with
512n sectors, don't care about alignment, but the biggest one
today is a 2TB 512n.
I have one drive here, which is a 4TB 512n, and that might well
be the highest capacity 512n drive made. The sectors internally
are 512 bytes. The sectors externally are 512 bytes. There are
no tricks or read-modify-write involved with such drives, when
the file system is not aligned properly.
Properly supporting 512e drives, when they were invented, is why
we have real working cache designs in modern hard drives, and why
they can accept 1200-1400 commands per second (even though the
platter rotates 120 times per second). The drives in the old days
with 2MB or 8MB cache, those were mostly a bad joke -- the RAM was
at least partially used for the spare sectors table.
512e versus 512n (there aren't many 512n models left)
sudo fdisk /dev/sda
Welcome to fdisk (util-linux 2.37.2).
Command (m for help): p
Disk /dev/sda: 3.64 TiB, 4000787030016 bytes, 7814037168 sectors
Disk model: ST4000DM000-2AE1
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes <=== 512e drive, align partitions to power-of-two for best performance
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: FD3FB597-4327-44E8-9D4B-DD88747391CA
Device Start End Sectors Size Type
/dev/sda1 2048 1026047 1024000 500M EFI System
Command (m for help): q
mint@mint:~$ sudo fdisk /dev/sda
Welcome to fdisk (util-linux 2.37.2).
Command (m for help): p
Disk /dev/sda: 3.64 TiB, 4000787030016 bytes, 7814037168 sectors
Disk model: WDC WD4002FYYZ-0
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes <=== 512n drive, no alignment needed, "the way they USED to make drives"
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: CB193B17-CFCE-4E6B-A467-8627288B88B4
Device Start End Sectors Size Type
/dev/sda1 2048 206847 204800 100M EFI System
Command (m for help): q
*******
These are what the industry tells you to use. Whether the more
fancy drives are better in the long run, who knows. The caches on
these, are expecting write threads to be pointing all over the disk,
instead of the writes being "intelligently positioned". You would
want the largest cache possible on a disk like this, for best
longevity.
The fake drive label on these, indicate their intended application.
The real labels as shipped, have serial number and so on.
https://www.westerndigital.com/products/internal-drives/wd-purple-sata-hdd?null=&sku=WD11PURZ
The fake label on the Seagate, is more fluffy. This is their CCTV disk.
It basically matches their competitor.
https://www.seagate.com/ca/en/products/video-analytics/skyhawk-hard-drive/
Since the RPMs are not listed, this is likely a 5400RPM drive (consistent
with a 5.3W power consumption).
https://www.seagate.com/content/dam/seagate/en_ca/content-fragments/products/datasheets/skyhawk-ai-hm/skyhawk-3-5-hdd-DS1902-17-2107US-July-2021-en_CA.pdf
This is the Purple. It also does not list RPM, so I have to assume 5400RPM as well.
https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/internal-drives/wd-purple-hdd/product-brief-wd-purple-hdd.pdf
Disk RPMs
15000 Server disks 300MB/sec transfer rate (you cannot sleep in the next room, with these!)
10000 Velociraptor/extinct.
7200 Average home computer boot drive (WD Black) -- "real men use an SSD"
5400 Low power drives (backup drives can be this way)
5200
3600 The tat we used to buy :-) Just awful.
[Marketing People. Could we do without them ?]
The existence of this one, tells you there is nothing that special about the transport.
Notice it is 7200 RPM, unlike the others, and has a 512MB cache, and the firmware discipline is multi-thread cache for video. 6.3W, a bit more power usage.
550TB/yr, like a WD Gold of the same capacity.
WD Purple Pro WD181PURP 18TB 7200 RPM 512MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive
https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/western-digital/product/internal-drives/wd-purple-pro-hdd/product-brief-wd-purple-pro-sata-hdd.pdf
Yes, looks like Seagate has a response to that one. Maybe an Ironwolf Pro in sheeps frock.
Half the cache.
Seagate SkyHawk 3.5" 16TB HDD SATA Internal Hard Drive 7200RPM 256MB Cache
https://www.seagate.com/www-content/datasheets/pdfs/skyhawk-ai-DS1960-10C-2008US-en_CA.pdf
Summary: No one can afford to buy one, but the WD181PURP has some sweet specs.
I own 30 hard drives, but I could only afford to buy 1 Big One :-)
That's a Helium, to see how long the gas stays in them :-)
Paul
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