On Feb 12, 2010, at 8:20 AM, Felix Buenemann wrote:
> Hi Mickaël,
>
> Am 12.02.10 13:49, schrieb Mickaël Maillot:
>> Intel X-25 M are MLC not SLC, there are very good for L2ARC.
>
> Yes, I'm only using those for L2ARC, I'm planing on getting to Mtron Pro 7500
> 16GB SLC SSDs for ZIL.
>
>> and next, you need more RAM:
>> ZFS can't handle 4x 80 Gb of L2ARC with only 4Gb of RAM because ZFS
>> use memory to allocate and manage L2ARC.
>
> Is there a guideline in which relation L2ARC size should be to RAM?
Approximately 200 bytes per record. I use the following example:
Suppose we use a Seagate LP 2 TByte disk for the L2ARC
+ Disk has 3,907,029,168 512 byte sectors, guaranteed
+ Workload uses 8 kByte fixed record size
RAM needed for arc_buf_hdr entries
+ Need = ~(3,907,029,168 - 9,232) * 200 / 16 = ~48 GBytes
Don't underestimate the RAM needed for large L2ARCs
-- richard
>
> I could upgrade the server to 8GB, but that's the maximum the i975X chipset
> can handle.
>
> Best Regards,
> Felix Buenemann
>
>
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