Boot drives PCI-e SSD boot drives vs SATA III (SSD and rotating)
Assembled cognoscenti; on the off-chance someone is interested in fast boot-drives; (yes I know; if one doesn't boot down, one doesn't need to boot up ! : - / ; just wondering if anyone has had experience with: PCI-e SSD boot drives vs SATA III(SSD and rotating). There is a comparison of a few of the former here at http://techau.com.au/review-revodrive-240gb-pci-e-ssd-vs-ocz-agility-3-240gb... thanks Rohan McLeod
On 30/12/13 15:15, Rohan McLeod wrote:
Assembled cognoscenti; on the off-chance someone is interested in fast boot-drives; (yes I know; if one doesn't boot down, one doesn't need to boot up ! : - / ; just wondering if anyone has had experience with: PCI-e SSD boot drives vs SATA III(SSD and rotating). hi
the SATA-SSD boot system is quick at about 7secs Steve
Steve Roylance wrote:
.................snip
the SATA-SSD boot system is quick at about 7secs I'm seeing SATA-SSD with read/ write transfer rates at about 500MB/sec eg http://www.sandisk.com.au/products/ssd/sata/
whereas the PCI-e SSD seem to have read/ write transfer rate at about 1000MB/sec eg http://techau.com.au/review-revodrive-240gb-pci-e-ssd-vs-ocz-agility-3-240gb... so I could expect a boot time of about 3.5 secs in the above case ? thanks Rohan mcLeod
On 30/12/13 21:05, Rohan McLeod wrote:
whereas the PCI-e SSD seem to have read/ write transfer rate at about 1000MB/sec
http://techau.com.au/review-revodrive-240gb-pci-e-ssd-vs-ocz-agility-3-240gb... so I could expect a boot time of about 3.5 secs in the above case ?
thanks Rohan mcLeod
hi boot drive is Samsung 840 Series SATA read/write of about 500MB/s http://www.centrecom.com.au/samsung-840-120gb-mz-7td120bw-25-ssd I have nfs server and clients running so the 7s is rather slow dmesg shows swap being activated at 4.6s Steve
Rohan McLeod wrote:
I'm seeing SATA-SSD with read/ write transfer rates at about 500MB/sec eg http://www.sandisk.com.au/products/ssd/sata/
whereas the PCI-e SSD seem to have read/ write transfer rate at about 1000MB/sec eg
http://techau.com.au/review-revodrive-240gb-pci-e-ssd-vs-ocz-agility-3-240gb... so I could expect a boot time of about 3.5 secs in the above case ?
Run bootchart2 / pybootchartgui. The output looks like this: http://cyber.com.au/~twb/tmp/boot.nfs-common/bootchart.pdf http://cyber.com.au/~twb/tmp/boot.klibc/bootchart.pdf The gap on the LHS is before bootchart started (i.e. the ramdisk). The top graph shows the overall I/O wait in pink. You can see in the klibc one that seconds 12 through 14 aren't related to I/O at all -- a faster disk won't reduce that gap. If you look at the third graph, the only place there's any pink (I/O wait) is in loop0. That might be an artefact of these being netboot hosts, but if true, then AIUI even though there's overall I/O wait (first graph), faster I/O would AT MOST only remove those pink bars in the third graph's loop0 process. Don't forget that these are timing only from when the kernel starts executing, meaning that EFI POST and the bootloader both have to run first. And EFI (and the AHCI driver or proprietary RAID card, and the whole LOM BNC) take for-fucking-ever to boot -- and they're reading from ROMs, so a faster SSD won't help there at all :-/ (If you're curious, I made those graphs last week to investigate why installing nfs-common makes xdm take a whole lot longer to come up on Debian 7, compared to cheating and using nfsmount(8klibc). The latter isn't a long-term solution because it has a stub rpcbind and a nonexisting lockd.)
Trent W. Buck wrote:
Rohan McLeod wrote:
I'm seeing SATA-SSD with read/ write transfer rates at about 500MB/sec eg http://www.sandisk.com.au/products/ssd/sata/
whereas the PCI-e SSD seem to have read/ write transfer rate at about 1000MB/sec eg
http://techau.com.au/review-revodrive-240gb-pci-e-ssd-vs-ocz-agility-3-240gb... so I could expect a boot time of about 3.5 secs in the above case ? Run bootchart2 / pybootchartgui.
...............snip
Don't forget that these are timing only from when the kernel starts executing, meaning that EFI POST and the bootloader both have to run first. And EFI (and the AHCI driver or proprietary RAID card, and the whole LOM BNC) take for-fucking-ever to boot -- and they're reading from ROMs, so a faster SSD won't help there at all :-/ Many thanks Trent; too much time watching Top Gear....brmm ...brmmm (read any time !); yes now that my plans for world domination, after acquiring a PCI-e SSD have been put on hold : - [ ; boot time obviously has significant over-heads unrelated to 'disk' I/O. Still in the future when topological quantum processors have reduced instruction execution time to effectively zero; do you think ROM, 'disk' and RAM I/O; may remain the significant constraints ?
regards Rohan McLeod
On 31/12/13 10:43, Rohan McLeod wrote:
Trent W. Buck wrote: ... Still in the future when topological quantum processors have reduced instruction execution time to effectively zero; do you think ROM, 'disk' and RAM I/O; may remain the significant constraints ?
When FRAM or similar non-volatile RAM finally gets here at competitive speed and price we can just freeze the runnning system and power off with the convenience of instant hot start, subject to all that motherboard preamble crap. ... Maybe we could just have an eternal very low power wait state. .. Arghh - peripherals wouldn't like that. Back to a m/b 15 sec waking yawn and a 7 sec boot.
participants (4)
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Allan Duncan -
Rohan McLeod -
Steve Roylance -
Trent W. Buck