Craig Sanders via luv-main
<luv-main@luv.asn.au> writes:
> On Wed, Jan 13, 2016 at 01:28:57PM +1100, Trent W. Buck wrote:
>> AFAICT the only reason SSHDs exist are:
>>
>> * Windows has nothing like bcache/l2arc; or
>
> it does. it's called ReadyBoost. Compared to bcache/flashcache or L2ARC
> for ZFS, it sucks. You can't just tell Windows to use an SSD (or
> partition thereof) to cache an arbitrary disk....well, in theory you
That sounds like the one they introduced back when USB keys were cool.
I don't think anyone seriously intends it for hybrid SSD/HDD usage.
"the maximum cache size per device is 4GB (Vista) or 32GB (Windows 7)."
> can but in practice Windows itself decides whether that option will be
> available by its own inscrutable and undocumented method.
It looks like the drive has to NTFS/exFAT/FAT formatted,
because ReadyBoost caches to a file, not a disk/partition.
> I discovered this just last week after upgrading my win7 games box to
> have an SSD as a boot disk, decided to try ReadyBoost for my main 2TB
> steam library drive (not an SSHD) so made a 40GB partition for it. No
> matter what I tried, I couldn't get windows to make the option available
> in its Disk Manager GUI - it was there, just greyed out.
See above re 32GB cap.
(Aside: the windows types I've asked about this indicate that they
actually use the hardware vendor's hybrid drive implementation,
e.g. Intel's.)
> I gave up and expanded the main partition...will have to manually move
> big games to the fast SSD, which works nicely - witcher 3 loads much
> faster off the SSD. More importantly, save games load in about 25
> seconds rather than 60-90 seconds (which is really annoying when you die
> repeatedly because you thought attacking a royal griffin seemed like a
> good idea, 90 seconds to load the save, 15 seconds to die again while
> trying to run away, repeat until you succeed or rage-quit)
I know at least one guy who netboots his Windows games machine off a
linux array, exported as iSCSI or something. I dunno where the
bottleneck is there, but it means he can snapshot the disk &c like it
was a VM.
>> * My computer only has one disk bay.
>
> (you don't really need a disk bay for an SSD. just a sata port plus data
> and power cables. and if you wanna get fancy you can sticky-tape it to
> the side of the case :)
I was handwaving that detail away;
I was specifically thinking of laptops with a single 2.5" bay and no M.2.
> but given that the SSHDs i bought were roughly the same price as
> non-SSHDs
Hrm...
$ msy | foldr grep -Fi -- 2tb 3.5 sata3 7200
135 Seagate 3.5" SSHD 2TB ST2000DX001 NAND 8GB SATA3 7200rpm 64MB Hybrid
HDD
98 Seagate 3.5" Barracuda 2TB ST2000DM001 SATA3 7200rpm 64MB Cache Hard
Disk
$ msy | foldr grep -Fi -- 4tb 3.5 sata3 5400
249 WD 3.5" SSHD WD40E31X 4TB 5400RPM SATA3 Hybrid (8G SSDHDD) NAND SSHD
202 WD 3.5" Blue 4TB WD40EZRZ 64M 5400RPM SATA3 HDD
$ msy | foldr grep -Fi -- 4tb 3.5 sata3 5900
329 Seagate 3.5" Enterprise NAS 4TB ST4000VN0001 SATA3 5900rpm 64MB Cache
HDD
275 Seagate 3.5" SV35 ST4000VX002 4TB 5900rpm Surveillance HDD include
Data Rescue Service
259 Seagate 3.5" NAS 4TB ST4000VN003 SATA3 5900rpm 64MB Cache HDD include
Data Rescue Service
239 Seagate 3.5" SV35 ST4000VX000 4TB 5900rpm Surveillance HDD
219 Seagate 3.5" SSHD 4TB ST4000DX001 NAND 8GB SATA3 5900rpm 64MB Hybrid
HDD
219 Seagate 3.5" NAS 4TB ST4000VN000 SATA3 5900rpm 64MB Cache HDD
185 Seagate 3.5" Barracuda 4TB ST4000DM000 SATA3 5900RPM 64MB Cache Hard
Disk
That's a ~20% markup on the first two.
SSDs start at A$60 for 120GB -- not much more than the difference.
>, i don't see any harm and some potential benefit in using them
> on linux. 8GB cache isn't much but it "just works" without any hassle
> or configuration. it's giving me some SSD caching on my ZFS 'backup'
> pool without having to add another SSD to the same andr dedicate an SSD
> partition to the task.
I guess that's reasonable.
What's the failure mode when the NAND wears out?
Does it detect that and fall back to being a regular HDD?
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