Re: non volatile ram devices

[Hans Reiser <reiser@namesys.com>]

Russell Coker wrote:

>I have some servers that are giving inadequate disk performance for Maildir 
>mail spools.  They are running kernel 2.4.19 (2.4.20 upgrade is planned) and 
>using ReiserFS for everything that's important.
>
>At this stage it is impossible for me to replace disks, RAID controllers, or 
>anything else really significant.
>
>What I am thinking of doing is using a kernel that supports data journalling 
>which should increase performance, but still probably won't give me enough.  
>So I am thinking of using an "external journal" (or using software RAID to 
>put the part of the partition containing the journal on a different device).
>
>The device containing the journal would be something much faster than physical 
>media.  I have been doing some research on non-volatile memory devices.  I 
>only found one company producing disks that are RAM based with battery 
>backup, and they seem to start at $10K (too expensive - probably because they 
>are much larger than I need, I need 128M at most, they provide 2G).  I found 
>many companies selling flash memory, but that only takes a million writes 
>(that'll last about an hour for the use I plan).  I found one company selling 
>PC-Card devices that have two batterys for backup, but that requires getting 
>a PCI controller for PC-Card's (something I haven't tried before).
>
>Does anyone know of an affordable ($1000 or less) device that can survive 
>unexpected power outages of at least 24 hours duration, can commit a write in 
>less than 1ms, supports unlimited writes, and connects to a IDE or SCSI bus 
>(or PCI if there's a suitable Linux driver).
>
>  
>
The umem.com folks sell a device that we have tested and benchmarked 
reiserfs on. If I could get Edward to format benchmarks in a way that 
conveys that information that is relevant to persons reading them, I 
would post them on our mailing list....

Hans