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Testing disks: Lessons from our odyssey selecting replacement SSDs

bbc.co.uk

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Re: Testing disks: Lessons from our odyssey selecting replacement SSDs

#21

Post by arethuza »

anoother wrote: post #12
tankenmate wrote: post #4

Earlier quoted context omitted.

The BBC has a very strong product prominence policy[0] (i.e. avoid naming brands when possible), being government funded is a large driver of this policy. [0] http://www.bbc.co.uk/editorialguidelines/guidelines/editoria... EDIT: fixed policy name and added link

It's a shame this is so selectively applied. See, for example: - The constant mention of speaking to people 'over Skype' on the News - Publicization of Twitter hashtags on Questiontime and other programs - Hours worth of Top Gear footage (and the entire Arctic Special) that were effectively Toyota Hilux advertisements

Isn't most of Top Gear about coverage of different automotive brands?

Re: Testing disks: Lessons from our odyssey selecting replacement SSDs

#23

Post by olavgg »

barrkel wrote: post #18

I built my home system early this year using the Samsung 960 Evo 1TB M2. Actual speeds were nowhere near advertised speeds until I enabled write-back cache on the drive, which gave me pause for concern about data persistence reliability. AFAIK the Samsung drivers (as opposed to the MS drivers I originally used) just turn this on without needing to be twiddled in settings. Just to confirm, I have seen the behaviour de…

I also have a Samsung 960 Evo. Its performance is what I consider a joke, fio and pg_test_fsync make it almost look as slow as spinning SAS drives.

For example on a 4kb sync write with 16 threads test, the 960 Evo cannot do more than 1000 iops. In comparison the Intel P4800X (Optane) does friggin 500 000 iops on the same test. That is a 500X difference.

https://forums.servethehome.com/index.php?threads/did-some-w...

Re: Testing disks: Lessons from our odyssey selecting replacement SSDs

#24

Post by dboreham »

marbletiles wrote: post #20
afandian wrote: post #10

Earlier quoted context omitted.

(This is almost too petty a point to reply, but "sticky backed plastic" is a sheet of adhesive transparent film, like you'd use to cover books. I think they probably would have said "sticky tape")

They literally did say "sticky-backed plastic" for sellotape, which left me bemused as a nipper

Especially bemused because that's not what they meant. SBP is Fablon or plastic film that comes in a wide (2+ ft) roll and is primarily used to cover books.

Re: Testing disks: Lessons from our odyssey selecting replacement SSDs

#25

Post by wtallis »

barrkel wrote: post #18

I built my home system early this year using the Samsung 960 Evo 1TB M2. Actual speeds were nowhere near advertised speeds until I enabled write-back cache on the drive, which gave me pause for concern about data persistence reliability. AFAIK the Samsung drivers (as opposed to the MS drivers I originally used) just turn this on without needing to be twiddled in settings. Just to confirm, I have seen the behaviour de…

Microsoft's NVMe driver is generally regarded within the storage industry as a bad joke. The fact that it has very different cache control behavior from their SATA driver despite the two using the same check box and same help text is really inexcusable.

Re: Testing disks: Lessons from our odyssey selecting replacement SSDs

#26

Post by nickcw »

This is the problem IMHO

> We also looked up whether our HBA used TRIM in its current configuration. It turns out, in RAID mode, the HBA did not support TRIM. We did do some trim-enabled testing with a different machine, but these results are hard to compare fairly. In any case, we can't currently enable TRIM on our production systems.

In our experience SSD write performance goes to sh*t if you don't regularly TRIM them.

Running fstrim once a day is enough to keep them healthy.

RAID cards not passing TRIM is a big problem for us too...

(Experience from day job at Hosting Provider)

Re: Testing disks: Lessons from our odyssey selecting replacement SSDs

#27

Post by equalunique »

pxlfkr wrote: post #22

Plugging SATA drives into a SAS HBA may not be optimal: "SAS/SATA expanders combined with high loads of ZFS activity have proven conclusively to be highly toxic" http://garrett.damore.org/2010/08/why-sas-sata-is-not-such-g...

Interesting. This may explain a strange incident that I once encountered. One day I came home to my CSE-847 machine with SATA drives hooked to SAS expanders on an mpt device. The whole system was unresponsive and the drives were all as hot as a fresh pot of coffee. I immediately shut down the system and let the drives cool out on the concrete floor. Everything seemed to work later, but it was quite a scare. It was 12 2TB drives setup as 6 zraid2 mirrors.

Re: Testing disks: Lessons from our odyssey selecting replacement SSDs

#28

Post by anoother »

arethuza wrote: post #21
anoother wrote: post #12

Earlier quoted context omitted.

It's a shame this is so selectively applied. See, for example: - The constant mention of speaking to people 'over Skype' on the News - Publicization of Twitter hashtags on Questiontime and other programs - Hours worth of Top Gear footage (and the entire Arctic Special) that were effectively Toyota Hilux advertisements

Isn't most of Top Gear about coverage of different automotive brands?

It is. I'm referring to:

- A running gag that, iirc, covered multiple seasons, about the 'indestructibility' of a red 90s Toyota Hilux. Performing destructive stunts and then driving away with minimal/no repairs. No other cars were involved in this segment.

- A special, hour-long episode involving a grueling trip to the pole in a fleet of brand new, red Toyota Hiluxes.

Whichever way you look at it, this was fantastic advertising and brand reinforcement for Toyota.

Re: Testing disks: Lessons from our odyssey selecting replacement SSDs

#29

Post by dr_ick »

barrkel wrote: post #18

I built my home system early this year using the Samsung 960 Evo 1TB M2. Actual speeds were nowhere near advertised speeds until I enabled write-back cache on the drive, which gave me pause for concern about data persistence reliability. AFAIK the Samsung drivers (as opposed to the MS drivers I originally used) just turn this on without needing to be twiddled in settings. Just to confirm, I have seen the behaviour de…

Watch the following video that explains why the 960 EVO has poor write performance after exhausting its cache:

https://youtu.be/RqaZTwW_X2o?t=511

For sustained write performance you need the 960 PRO.

Re: Testing disks: Lessons from our odyssey selecting replacement SSDs

#30

Post by wtallis »

olavgg wrote: post #23
barrkel wrote: post #18

I built my home system early this year using the Samsung 960 Evo 1TB M2. Actual speeds were nowhere near advertised speeds until I enabled write-back cache on the drive, which gave me pause for concern about data persistence reliability. AFAIK the Samsung drivers (as opposed to the MS drivers I originally used) just turn this on without needing to be twiddled in settings. Just to confirm, I have seen the behaviour de…

I also have a Samsung 960 Evo. Its performance is what I consider a joke, fio and pg_test_fsync make it almost look as slow as spinning SAS drives. For example on a 4kb sync write with 16 threads test, the 960 Evo cannot do more than 1000 iops. In comparison the Intel P4800X (Optane) does friggin 500 000 iops on the same test. That is a 500X difference. https://forums.servethehome.com/index.php?threads/did-some-w...

The 960 EVO is a consumer grade SSD with firmware tuned for bursts of I/O (through eg. the use of SLC write caching) at the expense of sustained write throughput. It doesn't have power loss protection capacitors, so it can't perform safe write caching when you're issuing synchronous writes. 4kB is much smaller than the underlying page size of its NAND flash, so performance is going to suck without write combining. You're testing it in shackles, with a workload that doesn't at all match its intended use case. That doesn't make it a joke, it just makes it the wrong kind of drive to use for stereotypical enterprise applications.
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