Yep, doing a 200 GB database with high-end and reduntant SLC NAND is definedly
not cheap (let alone the 2 TB Bill Colwell described in his post). Not that
bunch of 15K disks and the power to run them is free, either. Cost per IOPS for
disk is actually terrible.
Just a thought (don't take too seriously!): what if you'd be willing to take
the risk and forget RAID/mirroring, after all solid state is pretty reliable
these days. Of course - in addition to perfect DB backup strategy you need
anyhow - put your transaction logs to different disk: spinning disk is great
for that (it's more or less sequential I/O). And maybe even use cheaper MLC
NAND - if you "short stroke" (google for intel ssd overprovisioning) a 160 GB
X25-M down to 128 GB, you get three times the endurance, so it should last for
quite a long time even with DB workload. Of course, like tapes, you have to
treat NAND media as consumables, and keep an eye on the S.M.A.R.T. media
wearout indicators.
Yeah, too radical and risky for most. We'll just have to wait for couple of
years more to finally get rid of rotating rust for random IO usage once and for
all.
On Nov 22, 2010, at 7:13 PM, Pretorius, Louw <louw AT sun.ac DOT za> wrote:
> Well as I was specing a new TSM server i thought, why not try for the best
> performance possible and although the SSD drives drives the server costs up
> by 50% it wasn't out of the ballpark, therefore I wanted to hear from the
> community what their ideas were.
>
> As it stands I have a 100GB DB currently ~50% used but according to IBM TSM
> 6.2 will require double DB size hence 200GB and since we are expecting a 40%
> data-growth next year and will be implimenting Dedupe I thought why not see
> how the price/performance goes on other sites.
>
> As db2 is a fully featured DB I thought that the alternative would be to give
> it more RAM, as it's so much cheaper than SSD's. And also how I could
> configure my DB2 to use the extra RAM that I will be throwing at it in any
> case.
>
> With the current feedback I will be sticking to 6 x SAS 15K and 24GB RAM...
>
> Please if there's any other opinions let's hear it, the more opinions the
> more wisdom...
>
> Regards
> Louw Pretorius
>
> -----Original Message-----
> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf
> Of Henrik Ahlgren
> Sent: 22 November 2010 11:25
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: Re: [ADSM-L] DB2: SSD vs more RAM
>
> Or maybe he has a huge amount of DB entries? If his options are either six
> SAS 15K or eight SSDs (50GB each), it means his DB is propably in the
> multi-hundred gigabyte range. If he just needs the IOPS for smaller DB, then
> he would not need 8 SSDs to beat 6 platters, even one or two could be enough.
> (Just one Intel X25E does 35K IOPS random 4K read.) I'm not sure how much
> doubling the RAM would help with operations such as expiration, DB backup
> etc. compared to nice SSD setup.
>
> I'm wondering why so little discussion here on using solid state devices for
> TSM databases? Some of you must be doing it, right?
>
> On Nov 17, 2010, at 7:50 PM, Remco Post wrote:
>
>> SSD to me seems overkill if you already have 24 GB of RAM, unless you need
>> superfast performance and are going to run a very busy TSM server with a
>> huge amount of concurrent sessions.
>>
>> --
>>
>> Gr., Remco
>>
>> On 17 nov. 2010, at 12:16, "Pretorius, Louw <louw AT sun.ac DOT za>" <louw
>> AT SUN.AC DOT ZA> wrote:
>>
>>> Hi all,
>>>
>>> I am currently in the process of setting up specifications for our new
>>> TSM6.2 server.
>>>
>>> I started by adding 8 x SSD 50GB disks to hold OS and DB, but because of
>>> the high costs was wondering if it's possible to rather buy more RAM and
>>> increase the DB2 cache to speed up the database.
>>>
>>> Currently I have RAM set at 24GB but its way cheaper doubling the RAM
>>> than to buy 8 x SSD's Currently I have 8 x SSD vs 6 x SAS 15K
>
>
> --
> Henrik Ahlgren
> Seestieto
> +358-50-3866200
--
Henrik Ahlgren
Seestieto
+358-50-3866200
|
