Re: SSD as Cache?
Sorry,
/sbin/udevadm info --query=property --name=sdb |grep ID_MODEL
ID_MODEL=M4-CT128M4SSD2
MTBF 1,2 Mio h = 500000 days = 136,98 years
Drive Endurance 72TB=40GB per day for 5 years
I will try to measure the "traffic" next week.
There are Hosted Servers, they are changed every 2 years to "new hardware".
Here are Dedicated Root Servers.
The Webapplication Files (PHP and so on are on RAID), also the Postgres
Data-Dir.
The Root Partition is on SSD, also /boot and swap.
The Images are on SSD, "mounted via bind".
The System has 32GB RAM and thats mainly used for Postgres cache and
MongoDB.
There is a Backend Postgres Database Server that cluster to this
Frontend Server.
So that this Frontend / Application Server can work "standalone".
The mongoDB "cache" the Postgres Querys and some json Objects for the
Application. Serialized Arrays and so on.
When this crash it doesn't matter, It only takes longer to display the
Webpages.
I think 20-30 GB will be free on SSD when it's used as Cache, even more.
(Thats my personal limit, that should be free on system disk.)
Basti
Am 08.11.2013 16:04, schrieb Paul Johnson:
> How many writes is the SSD rated for?
Am 08.11.2013 20:26, schrieb David Christensen:
> On 11/08/2013 06:12 AM, basti wrote:
>> on my Webservers,
>
> "Webservers" is plurar. Is there a database server? A file server? How
> many servers do you have? Real or virtual? What is the topology? Is
> this on the public Internet?
>
>
>> I have 1x 128GB SSD and a Raid 1 (1TB).
>> Now I plan to improve the performance of my Webapplication.
>> The Cache is about 10.0 GB in 2000000 files.
>
> I'll assume the OS and application are on the SSD, and the application
> data and cache are on the RAID.
>
> How is the SSD partitioned? Make/ model/ version? Interface/
> motherboard make/ model/ version? Any free space?
>
> Tell us about the RAID. Hardware or software? Makes/ models/ versions
> of drives/ interfaces/ software? File system? Any free interfaces,
> drives, and/or space?
>
> 2E+06 files totaling 10 GB is a lot of small files. You will want a
> dedicated partition with a file system created/ tuned for this purpose.
> If your cache is not on such already (e.g. two 1 TB desktop HDD with
> LVM RAID 1 and default ext4 files system), this may be your bottleneck.
>
>
>> Can this cache moved to SSD?
>
> I would think so, if the application allows it and there is room on the
> SSD.
>
>
>> Months ago I read articles about SSD and Flash Memory like:
>> - "Disable logging on SSD"
>> - "Disable cache on SSD"
>> - "Don't swap on SSD" ...
>> And today?
>> How long will the SSD work without data loss?
>
> The questions of 1) whether or not it will help and 2) whether or not
> it's going to wear out your SSD are difficult to answer a priori without
> intimate knowledge of your hardware, software, and usage patterns. The
> simple answer is "go for it" for a week and see what happens.
>
>
> It would help if you provided:
>
> - hardware make/ model information.
>
> - OS and software name/ version information
>
> - system monitoring data -- CPU, RAM, cache, swap, drive, network, etc.,
> usage, bandwidth, etc., for a typical usage period (1 week?).
>
> - other constraints -- network bandwidth, network aggregate data limits
> application source code and license, etc..
>
>
> David
>
>
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