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Thread: SSD vs SAS for performance




  1. #11
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    Default Re: SSD vs SAS for performance

    Login icon with password to done booting is 3 seconds. Vista x64 Ultimate uses all 8 cores for boot up.

  2. #12
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    Default Re: SSD vs SAS for performance

    hmm... ssd is a medium, while sas is an interface? So will SSD SAS be many times faster than SSD SATA?

    SSD is still a very niche market and there's still issues that need to get resolved. I guess for those who like no noise, no moveable parts, and does not require huge storage and willing to pay the price premium might want to go the SSD route.

    Regarding seek and throughput, in raid, probably when you have lots of disks running in parallel, the low seek time of the SSD might make some difference, but it also depends whether ya application can make the full use. Also note for raid environment, especially hardware raid, a lot of times the performance get max out at the raid controller level. I believe the fastest hw raid controllers are probably those running on the intel iop chip if not wrong.

    So again depends on ya application. If ya do datawarehouse database, low seek time is quite meaningless, and you probably want throughput. Aside from the raid controller limitation, you can max out the throughput probably with less disks using SSD vs SAS disks.

    In my case, I went for SSD for my laptop mainly i do no need the storage capacity, and I prefer non moveable parts for SSD and a little lighter and hopefully less heat as well.

  3. #13
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    Default Re: SSD vs SAS for performance

    SSD is cutting edge right now. In 2-3 years, they might solve their issues and be more mainstream. You are seeing them in highend laptops. In RAID, it could be an issue. I asked a few reviewers to test SSD in RAID to see how they perform and take the abuse of RAID.

    SAS drives have very low latency. I don't think a single user will see the difference for most things. Is saving 10 seconds on loading a game worth spending 2x the price for SSD. Most home users want a drive that has less issues. I use SAS for production projects that require performance and a drive that does not fail with the heavy IOs.

    You pay a lot for little return. It is not like if you take 5 minutes more all day for a home user that you lose money.

    My SAS RAID 1 drives are two drives. In RAID performance on most server grade controllers, you get lower return of performance after 6-8 drives. Only on $50,000+ SAN with dual channel drives and two cached controllers per drive does over 8 drives gain in performance. For home users, I don't know many with more than 8 drives. I did have 16 SCSI drives at one point in three RAID arrays. The newer SAS drives will cut that to 6.

  4. #14
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    Default Re: SSD vs SAS for performance

    I am going to move this thread to the storage section since it has moved far away from a Runcore discussion.

    As someone with a bunch of solid state drives and eleven 15K.7 600GB drives I can tell you that modern SSDs are faster for most tasks by a pretty large amount. Seagate will tell you the same thing. Then they will tell you how hard they are working on getting their SSDs ready.

    If you want to get the best of both worlds look into the Adaptec MAXIQ system. This uses SATA/SAS drives and an Intel SSD.

    Making blanket statements like SAS has lower latency is not truthful. I have a Seagate 7,200 RPM SAS drive and it has just as much latency as any other 7,200 RPM drive. Rotational latency can't be scrubbed off just because you have a controller with 2GB of cache. You know what your system feels like with a 15K drive with 5 ms access time compared to a drive with 12 ms access time. Do you really thing there isn't a difference once you get to .15 ms access time?

    If you really don't think you can see a difference then you need to go out and buy a drive and see for yourself.

    Coming out and saying that you are already seeing people with SATA 6Gb drives having issues is a stretch as well. I have two drives here and have been running them nearly 24/7 since the arrived and have yet to run into a single issue, RAID or JBOD. Most reviewers just got theirs a week or so ago and I don't see many people going out and spending 300 USD on a drive and a P55 board to run them. The people that will spend 300 on a 2TB drive are already running X58 systems and will laugh about the downgrade to P55. I have yet to see a U3S6 card listed for sale either (but I am testing one now). This will be the way most enthusiasts go for early SATA 6Gb until we see chipsets from Intel with SATA 6Gb.
    Last edited by chrisram; 11-19-2009 at 04:12 AM.

  5. #15
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    Default Re: SSD vs SAS for performance

    I agree chrisram. 99.9% of people who I hear saying that SSD's make no difference or aren't worth it have never experienced the speed and responsiveness of a second gen (Samsung, Intel or Indilinx based) SSD.

    Latency makes a huge difference. It's not like you sit there counting latency, sure. 4ms sounds like nothing, and one could never count to 4ms mentally. However SSD's latency is minute compared. My average write latency is 0.079ms. All this adds up to higher random transfer rates. Random read and write is the bread and butter of what an OS does with a disk. Nobody sits there transferring 10GB files sequentially from one drive to another all day, unless running some kind of Blu-Ray replicating operation etc.

    Even the fastest HDD gets bogged down when loads of small reads and writes are being concurrently requested. This is where a SSD shines. I did a test weeks ago for a write up on SSD's I'm authoring. In this test I exacuted a script to open 5 programs at the same time. This was done at boot the very second that the desktop appeared. No time was allowed for the machine to settle down or for the HDD churning that happens at windows load on a mechanical drive to stop. The test HDD (WD6400AAKS, not the quickest but decent) completed the task in around 50 seconds, as it was heavily bogged down. Basically it didn't know what the heck to do with all the incoming requests for a mix of random and sequential small file reads and writes. The SSD (Intel X25-M) completed the task in 8 seconds. That says it all IMO.

    Until Intel release their next ICH, hopefully the ICH11 and ICH11R, or possibly integrated onto CPU's in the future, SATA 6G effectiveness may vary slightly depending on controller manufacturer. At the moment there are a few manufacturers with different controllers out. Who knows if these vary in performance by much. There is no drive yet able to transfer at SATA 6G speeds other than with burst speed unfortunately. SATA 6 will really let SSD's stretch their legs when the SSD controllers arrive. Intel usually do a pretty decent job with their ICH's. Saying that SATA 6G will be poor compared to anything else isn't really fair as nobody has seen what it can really do.

    Looking forward here to SATA 6G affordable RAID cards. From what I hear, the I/O processors are stronger than those used on SATA 3, meaning possibly that the throughput limit will be higher than the Intel ICH limit of approx ~650MB/s. That sounds a lot, but as soon as you get to 4 SSD's, especially on sequential reads, the controller bounces around on its limit. There are of course some really nice RAID cards available but I can't really afford to treat myself to 4 SSD's for RAID0 and also get a RAID card. I have seen figures of over 1700MB/s using I think 8 OCZ Vertex 30GB drives. Atto was all over the place on the 16K and 32K size tests, but that may have been a benchmark hiccup.

    I'm not saying that SSD's are suitable for everyone. Also SSD controller manufacturers, driver writers, ICH makers and OS programmers need to put there heads together and make sure that TRIM is being implemented correctly. It's actually pretty hit and miss for some at the moment. Not broken, but inconsistent. Some users have no issues at all, others do. You have to keep an eye on performance without constantly benchmarking day in and day out.

    Given the choice I'd never go back to a mechanical drive for my OS and programs. When TRIM is 110% sorted and prices come down for larger capacities, I'll quite happily go all SSD unless I happen to need a drive with a couple of TB's of space.
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  6. #16
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    Default Re: SSD vs SAS for performance

    TRIM is really what is holding everything back right now. I am writing an article on it right now, Cameron has been after me to get it done for a month now.

    If you are running RAID you will not see Win 7 TRIM doing anything for you. The Intel SATA driver still breaks Win 7's TRIM support as well. I hate to say it but if you want to run RAID the best you can get is the Samsung controller since it has garbage collection in the hardware. The down side is you need to run your system 24/7 to see any performance being recovered since it is darn slow.

    Indilinx has really impressed me with their TRIM support for a single drive in Win 7 but given the choice most enthusiasts will want to spend the same amount of money on two 128GB drives instead of a single 256 and run the 128 drives in RAID. We have been publishing some really good reviews of drives in RAID 0 when the assets are available.

    I have the LSI SATA / SAS 6Gb controller that was used with the 8 OCZ drives, AMAZING performance. My last 8 15K.7 drives just arrived yesterday and I can't wait to see how they perform on the controller but my 8 drive 7200.11 array was pretty weak and I expected more from a PCIe 2.0 controller with 8 drives.

    This is a very exciting time for storage guys right now. It took more than a year to get burst speeds that took advantage of SATA. SATA II was pretty much the same way but here we are now with the 15K.7 saturating SAS 1.0 and the PhotoFast V5 doing the same to SATA 3Gb. By January we should start to see Sandforce and Marvell controllers taking advantage of SATA 6Gb! At this pace we will need SATA 12Gb in three years.

  7. #17
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    Default Re: SSD vs SAS for performance

    Atto was all over the place on the 16K and 32K size tests, but that may have been a benchmark hiccup.
    ATTO is now useless now that we are getting reads and writes over 1K MB/s. I have been using it for many years and my heart sank (and my head was twisted) the first time it reported back a zero in the reporting field. I don't see ATTO as a company updating the benchmark but I could be wrong.

  8. #18
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    Default Re: SSD vs SAS for performance

    When running SSD's in RAID, OCZ Vertex/Agility with FW 1.41 is great. A couple of people I know have hammered their RAID array, and after letting 1.41 do its stuff, have seen performance turn around and improve. It's more gradual sometimes than you'd expect, with the first session restoring a huge chunk of speed and then things steadily improving over time. Vertex turbo 1.3 also has GC, but it's aggressively tuned,like the beta's. Their 1.4FW is TRIM, 1.41 just has Garbage Collection and Block consolidation. As with Samsung controllers, leave the PC to idle, either logged off, in S1 sleep (not S3 as it cuts power to the drive) or even at the BIOS screen if you really want to make sure there's zero disk activity. Logged off should be fine though. The only negative is the possible impact GC and BC combined may have on cell wear. Consolidating blocks will use up cycles. OCZ tuned their final release of 1.41 to be less agressive than the 1.41 beta for this concern. Not that I'm all that unduly worried about drive life.

    The other alternative would be to go with either Intel X25-M's or X25-E's. neither the G1 or G2 MLC or the only version of the SLC benefit much as they simply don't slow down very much. For instance th X25-M G2 maintains its sequential write flawlessly and its 4K random write drops from 36MB/s to 35MB/s on a completely "dirty" drive with no clear flash blocks left. In fact the only real reason I see for the TRIm FW on Intel drives is to get the increase in write speed that they included for the 160Gb X25-M G2.

    A personal preference but I'd much rather have to backup the array each month, take it down, Run Diskpart "Clean" and Sanitary Erase, then restore the image than buy a Samsung drive. Not that there's anything extremely wrong with Samsung based drives but their 4K random performance isn't stellar. Although it is still 3 times (very roughly) as fast as a mainstream HDD. Samsung drives can also ship with a couple of different firmware revisions, a few of which don't contain GC. The Samsung branded ones and the OCZ Summit, Corsair P series etc shipping now do. Only way to get the drive updated currently is to return it to the vendor as there's no flash tool been released to the public. Good old Samsung, a giant of the industry that does things only when they're ready.

    You make a good point about the enthusiast market going for multi drives to make the same capacity. I have a Vertex 30GB on the way to play with. If I find it satisfactory I'll be building up my collection of them, to 3 or 4. Being 30GB they're nice and cheep comparatively speaking.

    I say bring on the technology. Something like SATA revision is much easier to deal with due to the availability of add in cards. Remember the old Pentium Overdrives and those other adapters that allowed you to use the next gen sockets via a plug in PCB? Those days are long gone for most pieces of hardware now. Tech advances just move so fast.

    Looking forward to reading the article. It's good to get different perspectives on the issues from people who have different usage patterns etc.
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