Drive Failed, considering hybrid - what to look out for?

[ZVH]

Noticeably faster.
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I don't suppose you've ever run something like Black Magic on it have you:

https://itunes.apple.com/us/app/blackmagic-disk-speed-test/id425264550?mt=12

It's a freebee, but then again if the drive isn't working or it's failing, who knows how good the test results would be. I had some compatibility problems with that on Mavericks, but maybe they're fixed now.

 

[grahamperrin]

Overall performance of the Mac: better with the SSHD

Blackmagic Disk Speed Test

… something like Black Magic …

It's probably more than a year since I ran that. For what I used at the time (ZEVO, ZFS) the results were unrealistic because the Blackmagic tool issues F_NOCACHE calls which only apply to buffer cache (HFS+) but not to ARC (ZFS).

SpeedTools Utilities Pro

As far as I recall this, too, gave inaccurate results where ZFS was used.

I did use the QuickBench™ part of the suite in a different way, but I don't have the results handy.

Without using any such utility

Overall performance of the Mac was much better with the SSHD than with the HDD. Both had the same rotational rate.

 

[ZVH]

Blackmagic Disk Speed Test



It's probably more than a year since I ran that. For what I used at the time (ZEVO, ZFS) the results were unrealistic because the Blackmagic tool issues F_NOCACHE calls which only apply to buffer cache (HFS+) but not to ARC (ZFS).

SpeedTools Utilities Pro

As far as I recall this, too, gave inaccurate results where ZFS was used.

I did use the QuickBench™ part of the suite in a different way, but I don't have the results handy.

Without using any such utility

Overall performance of the Mac was much better with the SSHD than with the HDD. Both had the same rotational rate.

I have some questions about ZFS, since you've piqued my curiosity.

1. I did a little reading, and from a data integrity standpoint it sounds like it kicks butt, but all the cross referencing sounds like it's time consuming. How does ZFS perform compared to HFS or other file systems performance wise?
2. How would you say it's normally configured? Is it normal (or possible) to split a single drive in half and use one partition as the main scheme and the other as a backup, or is it preferable to use two drives?
3. Are the errors you're reporting in the previous post ZFS errors, because they're syntax looks a little strange to me?
4. How well adopted is this file system? I could see how this would be beneficial if not critical for servers, but would it make sense if there's a performance hit to use it on an end user system when it might simply be easier to just restore a backup?

It looks like an interesting file system, but it sounds like it would bottleneck the system overall (that's a guess, by the way).

Cheers.

 

[TheBSDGuy]

I doubt Apple would adapt ZFS for their end user systems. Maybe for OS X Server but I can't see it on an end user system.

There are rumors circulating that the next "improvement" is to completely hide the OS and all files completely from the user.

 

[grahamperrin]

… Are the errors you're reporting in the previous post ZFS errors …

No, the lines at https://forums.macrumors.com/showthread.php?p=20593395#post20593395 resulted from runs of fsck_cs

I should treat questions about ZFS as off-topic …

 

[ZVH]

No, the lines at https://forums.macrumors.com/showthread.php?p=20593395#post20593395 resulted from runs of fsck_cs

I should treat questions about ZFS as off-topic …

I guess you're right. I missed the part of your comment "For what I used at the time (ZEVO, ZFS) the results were unrealistic …" and thought maybe you had some type of configuration still using that.

If the drive is still functioning and it's using a more standard format it would be interesting to test the drives actual performance.

FWIW I used BlackMagic on a Fusion drive. It appears it takes samples across the volume. At one instance it would be returning very high speed results, indicating it was hitting the SSD, at other it would be hitting the HDD and you could tell because the data rate would drop. Another really dated tool I used was called Xbench. Support for that dropped some time ago but the drive speed tests still work. Newer versions of BlackMagic may address the oddity I described, I don't know.

With respect to a hybrid, what I'm wondering is whether SSD is a big, semi-permanent cache, with all the files stored in their entirety on the HD, or does it move active files off the HDD onto the SSD. To me, the cacheing model would be faster, but that's just an opinion.

 

[grahamperrin]

Solid state for cacheing or permanent storage

… With respect to a hybrid, what I'm wondering is whether SSD is a big, semi-permanent cache, with all the files stored in their entirety on the HD …

In a hybrid drive, the solid state is for cacheing.

In a hybrid volume, as defined in Wikipedia, the solid state is for permanent storage; not for cacheing.

Some dual-drive hybrid systems allow persistent cacheing.

 

[TheBSDGuy]

FWIW I used BlackMagic on a Fusion drive. It appears it takes samples across the volume. At one instance it would be returning very high speed results, indicating it was hitting the SSD, at other it would be hitting the HDD and you could tell because the data rate would drop. Another really dated tool I used was called Xbench. Support for that dropped some time ago but the drive speed tests still work. Newer versions of BlackMagic may address the oddity I described, I don't know.

With respect to a hybrid, what I'm wondering is whether SSD is a big, semi-permanent cache, with all the files stored in their entirety on the HD, or does it move active files off the HDD onto the SSD. To me, the cacheing model would be faster, but that's just an opinion.

If you run BlackMagic on a SSHD, it should return results similar to a hard drive. If the iterations were high it may eventually show SSD speeds as the cache might bump a less used file off the SSD and onto the HDD, and place the high access file on the cache. Normally that shouldn't happen with BlackMagic because it doesn't run that long.

With a Fusion drive a first write file may or may not be placed on the SSD depending on how full the drive is. It may be moved from the SSD to the HD or vice versa as it gets hit more frequently. Management in a Fusion drive is much more dynamic than it is with a hybrid.

 

[ZVH]

I found this benchmarking article interesting:

http://barefeats.com/hard176.html

I find the quote:

The Seagate SSHD "Hybrid" drive was not impressive compared to the regular HDD from Seagate.

The article is a few years old now, but the results more or less confirm BSD Guy's comment "If you run BlackMagic on a SSHD, it should return results similar to a hard drive" so basically, maybe it isn't occurring to the guy doing the test, he's just testing a hard drive. If the drive's rotational rate is 5400 RPM then that might explain the deficit compared to the standard hard drive, which does have a rotational rate of 7200 RPM. I took a quick look at Seagate's specs and they don't seem to like to mention the rotational rate of the hybrid drive.

 

[TheBSDGuy]

I'm fairly certain that Seagate's hybrids, or at least some of them, use 5400 RPM drives. Kind of like putting bicycle tires on a Ferrari, IMHO.

 

[ZVH]

…and here's there excuse:

http://www.seagate.com/tech-insight...e-storage-is-not-about-rpm-anymore-master-ti/

I think that's nonsense. Speed is speed. If Hitachi attached an SSD to their new line of high performance drives that run at 7200 RPM it would just be that much faster. The thing's already approaching SSD speeds, albeit slow SSDs, but pretty good for a hard drive.

 

[grahamperrin]

I'm fairly certain that Seagate's hybrids, or at least some of them, use 5400 RPM drives. …

Momentus XT Product Manual, Rev. D (PDF) suggests that when I made my choice, there were only 7,200 RPM models from Seagate.

System Information shows that I have ST750LX003-1AC154 revision SM12.

Choosing High Performance Storage is not about RPM any more | Seagate
(undated, from the earliest copy in the Internet Archive Wayback Machine I guess that it's around two years old)

"… Sometimes, however, data will be requested that is not in the NAND flash, and only during these instances does the HDD portion of the device become a bottleneck. Since the technology is so effective at identifying and storing frequently used data in the NAND area, SSHD technology is much more efficient in delivering data to a host computer quickly.

This result may be clearly observed by comparing the PC Mark Vantage storage scores of second- and third-generation Seagate SSHD technology and traditional 5,400 and 7,200 RPM HDDs. …"​

… I think that's nonsense. …

I haven't used PCMark Vantage (on Windows 7).

On a Mac with OS X, I always prefer a holistic approach to testing. That approach is not easily replicated by software.

For my use case, with 8 GB SLC NAND on the drive and 8 GB DDR3 memory in the MacBookPro5,2, I'm certain that 7,200 RPM was a good choice. (If a different manufacturer had offered a slower spinning SSHD, I would have preferred a faster spinning model.)

 

[TheBSDGuy]

I didn't research the spin of Seagate SSHDs, I believe I just remembered reading that from another post somewhere on here (not from you).

It would be nice if their specs provided some data about areal density and the maximum throughput from the SSD portion and the HD portion of the drive. It's probably out there somewhere. If they're using 5400 RPM drives in some of the SSDs I'd speculate that it's probably to lower costs.

Considering many people these days have terabytes of data, pure SSDs for many aren't a realistic cost option, and an SSHD or Fusion is a good tradeoff for performance.

 

[WorkerBee2015]

I assume a Fusion is necessarily faster than a hybrid because the memory in a Fusion is usually much larger than it is for a hybrid. Most of the hybrids I'm looking at don't seem to have too much flash memory in them. The smallest SSD I can find to make a Fusion Drive is 64GB. I'm sure I could find smaller if I looked hard, but anything smaller than that seems to be old.

 

[grahamperrin]

Dual-drive hybrid systems, and more

Dual-drive hybrid systems offer multiple benefits

1. capacity

I assume a Fusion is necessarily faster … because the memory in a Fusion is usually much larger …

True. The greater amount of relatively fast storage can be put to good use.

2. systems integration

A storage system that is suitably integrated with the operating system can make more intelligent use of the faster storage hardware.

With Apple Core Storage as a storage system, Fusion Drive involves movement of data from hard disk to solid state. If the connection is disturbed, the Mac goes down.

With ZFS as a storage system, one of the uses of faster storage hardware can be L2ARC – Level 2 Adaptive Replacement Cache. Where that faster hardware is solid state:

• data is copied, not moved, to the solid state
• the L2ARC device can be taken offline with a zpool command
• an offline L2ARC device can be disconnected then reconnected whilst the computer runs, and the computer continues to use the previously cached data
• if an online L2ARC device is accidentally disconnected, the computer does not go down.

Further reading:

• Persistent L2ARC - illumos - illumos wiki
• Aaron Toponce : ZFS Administration, Part IV- The Adjustable Replacement Cache (2012-12-07)

Seagate drive specifications

… if their specs provided some data about areal density and the maximum throughput from the SSD portion and the HD portion of the drive. …

Areal density and other information is in the Drive specifications section of the manual linked from my previous post.

Optimal use of faster storage hardware

From the Seagate manual:

"… The Momentus XT uses a proprietary algorithm which monitors drive activity and determines the optimum data to maintain in the NAND Flash for peak responsiveness. The Solid State Hybrid feature is self contained in the drive firmware and functions independent of the host hardware or operating system. There are no special host system requirements. Momentus XT can be installed in any standard SATA environment and will automatically optimize. …"​

Note: independent of the host hardware or operating system. That's quite different from the two storage system approaches outlined above.

 

[FrtzPeter]

The only problem I see with Core Storage is that it's like RAID. If one unit goes down, after finding the problem you have to do a complete restore because you never know what data is where at a given minute. As long as you have good backups the performance trade-off is probably worth it…for systems using an HD that is.

 

[grahamperrin]

Raid

… like RAID. If one unit goes down, after finding the problem you have to do a complete restore …

Not necessarily.

 

[TheBSDGuy]

To Graham Perrin:

Since you have actual experience with a hybrid, given the current options of SSD standalone, a hybrid, a Fusion Drive, or an older type mechanical HD, and knowing what you know now, would you buy another hybrid, or would you switch to something else?

 

[grahamperrin]

… would you buy another hybrid,

Yes.

or would you switch to something else?

With my plan to get a new (current) MacBook Pro, before Yosemite becomes a requirement:

• I have no choice, it's solid state
• the 2015 model will have less storage than the 2009 model because the cost of solid state is so much higher (it's not my own money).

 

[ZVH]

On topic:

Have you ever used a Fusion Drive, and if you did, how did it compare to a hybrid? From all the posts in this thread you're the only one that seems to actually have used one, but I don't know if you've ever played with Fusions. Personally, I like them. I also like the idea of daisy chaining several drives into one volume. I know it's been around on Unix/Linux/BSD for years and I've used it, but the idea of an SSD coupled with HD's for mass storage is one I like.

Off topic:
If someone forces me to use Yosemite, I swear to God, I'll quit my job! I swear to God, that stupid "nursery school" appearance (got that from one of the reviews at the App Store) is bad enough, but the bugs are unbelievable. I use Yosemite about 1-2 hours a day and today when I brought up System Preferences to change boot partitions on a system, it locked up for no apparent reason. The wi-fi is sketchy, depending on the system being used, and a fair number of applications either don't work or they crash. TextEdit crashing for no apparent reason???? Seriously???? When editing a basic text flle?????? Apple is finally making Linux and Microsoft look good!!!!

 

[grahamperrin]

Performance

… Have you ever used a Fusion Drive

No.

I could have taken a dual drive approach (with removal of the optical drive from the MacBook Pro) but I preferred to keep the optical.

… how did it compare to a hybrid?

I'm certain that a Fusion Drive, or ZFS with solid state for L2ARC, will be faster than a solid state hybrid drive. With Wikipedia as a starting point I found a few relevant items.

Computer Science & Engineering at OSU - Departmental News

"… three researchers published and presented a paper entitled "Hystor: Making the Best Use of Solid State Drives In High Performance Storage Systems" in the 25th ACM International Conference on Supercomputing (ICS 2011) …"​

– I recommend reading at least part of that paper.​

Momentus XT: Best Hard Drive Ever? - Momentus XT 750 GB Review: A Second-Gen Hybrid Hard Drive (2012-02-08)

"… Its hybrid nature necessitates performance evaluation across multiple runs of testing. …"​

Achieving fusion—with a service training doc, Ars tears open Apple’s Fusion Drive | Ars Technica (2012-11-06)

Page six of AnandTech | A Month with Apple's Fusion Drive (2013-01-18)

https://discussions.apple.com/message/26759690#26759690 refers to Hybrid drive versus HDD, SSD, and Fusion (2013-12-09); that discussion in Apple Support Communities goes on to question the value of the 2013 article.

Fusion Drive last words (2013)

… daisy chaining several drives into one volume …

With ZFS, Btrfs or something else?

 

[TheBSDGuy]

Off topic:
If someone forces me to use Yosemite, I swear to God, I'll quit my job!

Whoooooooa son, Whoooooooa. Calm down.

 

[nudoru]

I haven't read all 3 pages here, but ..

I've had a Seagate's hybrid's - the 500xt (the very first one) and the 750xt. In typical usage they're a little faster - boot and opening apps is definitely faster over time (it's learns from frequently accesses data). But generally, they weren't as fast as I'd hoped they would be. I ended up getting a Samsung SSD and putting a HD in my optical bay. Nothing can beat that

IIRC, the blackmagic numbers were in the upper 40's - close to 50.

 

[ZVH]

With ZFS, Btrfs or something else?

They were Sun Microsystem units so I suspect it was ZFS. I've also done some stuff with AIX and Silicon Graphics (now defunct) but that was so long ago I can't recall the details.

noduru:

Thanks for the input. I'd like to see this thread get as many perspectives on SSDs, SSHDs, Fusion Drives, and even higher speed hard drives as possible. I don't own this thread though….. but it would be great if this could be turned into some type of reference thread for people interested.

 

[nudoru]

noduru:
Thanks for the input. I'd like to see this thread get as many perspectives on SSDs, SSHDs, Fusion Drives, and even higher speed hard drives as possible. I don't own this thread though….. but it would be great if this could be turned into some type of reference thread for people interested.

NP! A thread like that would be a great resource.

I'm selling my Samsung SSD and Seagate 750 cheap if anyone is interested in upgrades. Sorry for the plug but I'm saving for an iPad